Method for modelling customised earpieces

ABSTRACT

The present invention relates to a method for computer-controlled modelling of customised earpieces. These earpieces include housings for hearing aids, wireless or connected communication devices (headsets, mobile phones, personal agents), loud speakers, tinnitus masking devices, devices recording vibrations in the skull and transforming these into audio signals, voice recognition devices, earplugs, noise blockers with selective frequencies or sound levels, Man Machine Interface (MMI) products that enable clear communication even in the noisiest environments, or products related to wireless Internet applications. All these earpieces may be worn in the user&#39;s meatus and/or auditory canal. The invention also relates to a computerised system for manufacturing such customised earpieces. In particular, the invention is directed to a computerised system that models an earpiece based on a three-dimensional replica of the user&#39;s meatus and/or auditory canal.

[0001] This application is a non-provisional of U.S. provisionalapplication Serial No. 60/275,112 flied 13 Mar. 2001, which is herebyincorporated by reference in its entirety. It claims priority fromDanish patent applications no PA 2001 00346 filed on 2 Mar. 2001, PA2001 00519 filed on 28. March 2001 and PA 2001 01521 filed on 17 Oct.2001, which are hereby incorporated by reference in their entirety.

[0002] All patent and non-patent references cited in the application, orin the present application, are also hereby incorporated by reference intheir entirety.

TECHNICAL FIELD OF THE INVENTION

[0003] The present invention relates to a method for computer-controlledmodelling of customised earpieces. These earpieces include housings forhearing aids, wireless or connected communication devices (headsets,mobile phones, personal agents), loud speakers, tinnitus maskingdevices, devices recording vibrations in the skull and transformingthese into audio signals, voice recognition devices, earplugs, noiseblockers with selective frequencies or sound levels, Man MachineInterface (MMI) products that enable clear communication even in thenoisiest environments, or products related to wireless Internetapplications. All these earpieces may be worn in the user's meatusand/or auditory canal. The invention also relates to a computerisedsystem for manufacturing such customised earpieces. In particular, theinvention is directed to a computerised system that models an earpiecebased on a three-dimensional replica of the user's meatus and/orauditory canal. The system also provides for a number of operations andmodifications to be performed on the reproduction.

BACKGROUND OF THE INVENTION

[0004] Many existing applications, such as in-the-ear (ITE),in-the-channel (ITC), or completely-in-the-channel (CIC) housings forhearing aids and personal communication devices (mobile phones orheadsets) require the reproduction of one-of-a-kind parts of complexgeometry. In these applications, the parts are unique and require ahighly precise fit of the replacement part Sub-millimetre precision isfor example required for ITE, ITC or CIC hearing aid housings; thehousing Will otherwise cause inconvenience feedback, as well asirritation and possibly infection to the epidermis of the ear canal.

[0005] Existing methods to model and manufacture customised housings forhearing aids are very long and tedious processes. They introduce a greatdeal of uncertainty about the quality of the finished product. Theprocess typically implies the creation of an impression of the user'sear canal. This impression must be adjusted manually and a mouldreplicating the user's meatus is created from the impression, either inplaster, gel, or silicone resin. A polymerisable liquid synthetic resinis produced, poured into the mould and polymerised at least partially.If the desired product is a shell for an individually fitted hearing aidhousing, most of the liquid synthetic resin must be poured out of themould again, before it completely polymerises. The resulting shell isground to the desired size and appearance. The components must then befitted manually into the shell; this operation is often problem-prone,since the shell has been designed without taking proper account of thecomponents' shape and size.

PRIOR ART

[0006] U.S. Pat. No. 5,121,333, U.S. Pat. No. 5,121,334, U.S. Pat. No.5,128,870. U.S. Pat. No. 5,184,306, U.S. Pat. No. 5,027,281, and U.S.Pat. No. 5,257,203 (REGENTS OF THE UNIVERSITY OF MINNESOTA) describe amethod and apparatus for the automated reproduction of three-dimensionalobjects of complex and unique geometry. A computer acquires datadescribing an object and its surroundings, constructs a computer-basedthree dimensional model of the object from the data, superimposes anideal geometry on the computer-based model, alters the ideal geometry tofit the form and function required of the reproduction, and then guidesa milling machine in the fabrication of the reproduction.

[0007] WO 00/34739 (FAGAN ET AL.) concerns a method for manufacturinghearing aid shells involving the use of a specially adapted ultrasonicprobe head to safely measure the contours of the ear canal withoutcontact with the surface being measured. The recording of data in theear canal is made possible by filling the canal with a liquid andinserting the ultrasonic probe The scan data is processed by a computerand the data is used with a rapid prototyping set-up such as stereolithography, selective laser sintering, laminate object modelling,inkjet modelling, fused depositing modelling, 3D or any other systemthat produces real models from computer mathematical models tomanufacture the hearing aid shell. EP 0 516 808 (TØPHOLM & WESTERMANNAPS) concerns a method for computer-assisted manufacture of otoplasticsindividually fitted to the contours of the ear canal. According to thedescribed method a digital representation of the internal contours ofthe ear canal is used for the production of a hearing aid shell, and thedigital representation Is used to obtain a computer model, which can beused for manual location of the components of the hearing aid and fordefining the thickness of the shell's walls.

[0008] U.S. Pat. No. 5,056,204 (ASCOM AUDIOSYS AG) concerns a method forthe milling of hearing aids whereby the internal contours of the earcanal are recorded by a laser apparatus located outside the ear of theuser.

[0009] JP09103000A2 (RION CO LTD) describes a method for the productionof shell for ear-inserted hearing aids whereby a three-dimensional shapemeasuring instrument is used to measure the shape information of theexternal auditory meatus directly or using a an ear model sampled byusing a sealing member. Next, the shape information and information onthe shape of the components to be integrated into a shell for hearingaid are inputted to a computer, and an external shape or an internalshape of the hearing aid shell is decided. Afterwards, thethree-dimensional shape data of the external or internal shape decidedby the computer system are inputted to an optical moulding device andthe hearing aid shell is directly produced by an optical mouldingmethod.

[0010] WO 01/05207 (PHONAK AG) discloses a method for production ofotoplastics, whereby an impression of the shape of the individualauditory canal is taken in order to produce shells for hearing aidsimplanted in the ear that very precisely adapt to the individual shapeof the auditory canal and a hearing aid shell is produced by means of anadditive fabrication process such as laser sintering, stereolithographyor a thermojet process that is controlled by means of data pertaining tothe shape. The disclosure provides no information on how to model theotoplastics including the placement of components.

[0011] Just placing components (as mentioned in EP 0 516 808, TØPHOLM &WESTERMANN APS) or just cutting away parts of the original 3D model onlygive weak indications of the full earpiece and the result is likely tobe of low quality. Furthermore, these prior art methods do not disclosehow to model complex earpieces with more features.

[0012] While concepts for the computer-assisted modelling and subsequentdirect manufacturing of custom-fitted earpieces, especially hearing aidhousings, are mentioned in the prior art, none of the above-citedreferences directly discloses steps or operations, which may be involvedin the modelling process of such customised earpieces. Thus, there is aneed for a method and/or providing one or more such steps or operationsthat can be used in order to optimise the modelling and production ofcustomised earpieces. Such a method and/or system is provided accordingto the present invention.

SUMMARY OF THE INVENTION

[0013]FIG. 5 shows an overview of how the tedious manual process can becomputer-assisted or computer-controlled leading to faster production,lower cost and higher acoustic and physical quality. The processconsists of three main steps: 3D scanning of the impression/ear, virtual3D modelling of the earpiece and finally manufacturing. The inventionprimarily relates to 3D modelling of the original 3D model acquired bythe scanner as illustrated in FIG. 10.

[0014] The invention enables the virtual creation of a complete earpieceby arranging relevant components in relation to the 3D model usingcollision control, cutting away the unwanted parts of the 3D model andforming a surface, which connects components and the 3D model. Thecreation of the full earpiece facilitates a true evaluation of theproperties of the final earpiece, e.g. visual and acoustic propertiesand room for components taking into account the constraint by allsurfaces. Additionally the virtual creation of the full earpiecesenables the physical manufacturing of the full earpieces eliminating alarge number of costly manual post processing operations.

[0015] According to a first aspect of the present invention there isprovided a method for computer-assisted modelling of customisedearpieces comprising at least one part being individually matched to anauditory canal and/or a meatus, said method comprising the steps of:

[0016] a) obtaining a three-dimensional computer model, 3D-model, of atleast part of the auditory canal, said 3D-model having an outer surface,

[0017] b) initially arranging at least one component in relation to the3>D-model,

[0018] c) initially arranging a cutting curve or cutting surface inrelation to the outer surface of the 3D-model, said cutting curve orsurface dividing the 3D-model in an outer portion and an inner portion,

[0019] d) initially forming a connecting surface connecting the at leastone component and the inner portion of the 3D-model, said connectingsurface thereby being part of the 3D-model,

[0020] e) performing an evaluation of the arrangement of the at leastone component, said evaluation comprising a collision detection of theat least one component in relation to one or more parts of the 3D-modeland/or other components, and

[0021] f) adjusting the arrangement of the at least one component, thearrangement of the cutting curve or surface, and/or the formation of theconnecting surface based on the result of said evaluation.

[0022] An initial cut to divide the 3D model in an inner and outerportion is not mentioned anywhere in the prior art relating tocomputer-assisted 3D modelling of customised earpieces. Such an initialcut is used in the manual modelling of earpieces based on impressions.In contrast to the manual method one primary advantage of the methodaccording to the invention is that the initial cut performed on the3D-model is optimisable, since it can be changed during the adjustmentstep based on the evaluation step. This is not possible when modellingearpieces manually and the possibility of optimising the initial cut incomputer-assisted modelling of customised earpieces is mentioned nowherein the prior art The fact that the initial cut can be optimised makesthe method more flexible than the methods of the prior art.

[0023] According to the methods of the prior art, there is no guaranteethat the components actually fit into the earpiece. In contrast to thisthe present invention physically places the components in the earpiece(in a modelling operation) to make sure that there is space for thecomponents. According to the present invention, if there is too littleroom for the components, further rounds of optimisation can beperformed, the optimisation process can be repeated, material can beremoved from the shell or the initial cutting curve/surface can be movedto create more space. The initial cut, dividing the 3D-model in an innerand outer portion also makes it possible to make a visualisation of themodelled earpiece in a virtual ear. Such visualisation and optimisationfor appearance is not described in the prior art. The visual appearanceof an earpiece is very important for the wearer. Furthermore accordingto the present invention, there is provided a method for modelling thecomplete 3D earpiece with all its surfaces. The methods disclosed in theprior art fail to provide a disclosure of how to arrange a connectingsurface connecting the 3D model with the at least component and therebyfail to teach a method for modelling the complete earpiece. The factthat the complete modelling of a 3D-earpiece is rendered possible by theinstant invention, also makes it possible to make an optimisation of theacoustic properties of the earpiece in the computer prior to prototypingand assembling it. The fact that the complete earpiece can be modelledalso makes it possible to prototype the whole piece in one operationthus obviating the need for assembling the piece from several pieces,such as an earpiece and a faceplate. However, it is still possible toincorporate a faceplate into the modelling according to the invention ifso desired.

[0024] All 3D models irrespective of whether they are obtained byscanning an impression or by direct scanning of the auditory canaland/or meatus need to have at least the outer boundary of the piecemodelled in order to obtain a complete earpiece.

[0025] Furthermore, the possibility of optimising the placement of theat least one component and the connecting surface gives the possibilityof optimising the visual appearance of the piece in the arm.

[0026] In addition, an important advantage of the present invention isthat the earpiece is only manufactured (through rapid prototyping) onceit has been established that all the components of the earpiece arelocated in the optimum location.

[0027] The order of the steps of the method according to the inventioncan be any.

[0028] Examples of preferred orders include, but are not limited to a)b) c) d) e) f); a) c) b) d) e) l); a) c) b) e) d) f); a) b) e) c? d) f):a) b) c) e) d) f). A preferred order is a) b) c) d) e) f), because ithas turned out that by arranging the at least one component first, andarranging the cutting curve/surface with the aid of the at least onecomponent makes it possible to model an optimal connecting surface infewer steps and often to reach the optimal or at least an acceptableplacement of the connecting surface in just one round.

[0029] The adjustment process may include either the arrangement of theat least one component, the arrangement of the cutting curve or surface,or the formation of the connecting surface or it may include anycombinations of the arrangement of the at least one component, thearrangement of the cutting curve or surface, and/or the formation of theconnecting surface. It is preferred that when the arrangement of the atleast one component and/or the arrangement of the cutting curve orsurface has/have been adjusted, the formation of the connecting surfaceis adjusted.

[0030] According to an embodiment of the invention, the arrangement ofthe at least one component in relation to the 3D-model may comprisearranging the at least one component in relation to a component surface,and arranging said component surface in relation to the 3D-model. Here,the connecting surface may be connecting said component surface and saidinner portion of the 3D-model, It is preferred that the collisiondetection includes a collision detection of the component surface inrelation to one or more parts of the 3D-model.

[0031] The collision detection may further include a collision detectionof the mutual arrangement of the components themselves.

[0032] When arranging the components, it is preferred that the initialarrangement of the at least one component in relation to the 3D-modelcomprises arranging at least part of the components substantially at theinterior of the 3D-model.

[0033] It should be understood that it is also within the presentinvention to have the evaluation process including an evaluation of thearrangement of the cutting curve or surface and/or the connectingsurface.

[0034] It is preferred that the formation of the connecting surface iscomputer controlled or computer assisted. It is also preferred that theformation of the connecting surface comprises a lofting process, wherethe lofting process may comprise fitting a parametric surface to theboundary of the inner portion of the 3D-model and to the boundary of asurface defining an outer boundary of the arrangement of said at leastone component in relation to the 3D-model. Here, the outer boundary ofthe arrangement of said at least one component in relation to the3D-model may be defined by the outer boundary of the component surface.

[0035] It is also within an embodiment of the invention that theformation of the connecting surface comprises a filleting process of theedge or boundary of the inner portion of the 3D-model. Here, the outershell surface of the 3D-model may be given in a vertex representationwith the vertices being connected by triangles, and the filletingprocess may comprise removing at least part of the triangles in aneighbourhood around at least part of said edge and fitting a parametricsurface to the neighbourhood of the hole created by the removedtriangles.

[0036] According to an embodiment of the invention, at least part of theinner portion of the 3D-model is shelled. Here, the shelling process maybe part of a modelling process according to the present invention, andthe shelled inner portion may have an inner and an outer shell surface.

[0037] According to a preferred embodiment of the invention, the innerportion of the 3D-model at least partly comprises a representation of amodel of an earpiece.

[0038] In another embodiment of the invention the outer portion of the3D-model at least partly comprises a model of a virtual ear.

[0039] It should be understood that it is preferred that said one ormore parts of the 3D model in relation to which the collision detectionmay be performed comprise at least part of the inner portion and/or atleast part of the outer portion of the 3D-model. Here, said one or moreparts of the 3D-model in relation to which the collision detection maybe performed may comprise at least part of the inner shell surfaceand/or at least part of an inner surface of the virtual ear.

[0040] According to a preferred embodiment of the invention thecollision detection and the adjustment, process may be repeated untilthe collision detection fulfils a required minimum criterion.

[0041] It should be understood that the initial arrangement of the atleast one component and/or the cutting curve or surface may be performedin several ways in accordance with the present invention. Thus, theinitial arrangement may be performed manually or be computer-controlledor computer-assisted. The initial arrangement may be performed using afeature-based approach, in which features extracted from the obtained3D-model are used for the arrangement, or performed using asimilarity-based approach, in which the obtained 3D-model is compared toa number of stored 3D-models of previously generated optimised models.

[0042] When using a similarity-based approach a stored optimised3D-model may be selected as the most similar 3D-model and the initialarrangement of the at least one component and/or the cutting curve orsurface may be selected substantially equal to the optimised arrangementof the at least one component and/or cutting curve or surface of saidmost similar 3D-model. Here, the comparison of 3D-models and selectionof the most similar 3D-model may be computer-controlled orcomputer-assisted.

[0043] It should also be understood that according to the presentinvention, the adjustment of the arrangement of the at least onecomponent and/or the cutting curve or surface may be performed manuallyor be computer-controlled or computer-assisted. A computer-controlled orcomputer-assisted adjustment process may also or alternatively Includethe adjustment of the formation of the connecting surface. Theadjustment process of the arrangement of the at least one component,and/or the arrangement of the cutting curve or surface, and/or theformation of the connecting surface may be adjusted until no collisionis detected.

[0044] According to the present invention, the collision detection maybe performed in several ways. Thus, the collision detection may beperformed by manual inspection of the three-dimensional computer modelor the collision detection may be computer-controlled orcomputer-assisted.

[0045] In a preferred embodiment of the present invention a rule-basedapproach may be used for the arrangement of the at least one componentand/or the arrangement of the cutting curve or surface. Here, an objectfunction, f(v), may be used. The object function may be defined forexpressing the quality of the arrangement of the at least one component,and/or the arrangement of the cutting curve or surface, and/or theformation of the connecting surface. The object function may be anincreasing function of the number of detected collisions and may becalculated for each new arrangement of the at least one component and/orthe cutting curve or surface. It is preferred that the arrangement ofthe at least one component, and/or the arrangement of the cutting curveor surface, and/or the formation of the connecting surface may beadjusted until the object function fulfils a given minimum criterion.Here, the minimum criterion may be that the object function obtains aminimum value, or that the difference in the values of two successivelydetermined object functions is below a defined value. When using anobject function, different weights may be assigned to different detectedcollisions.

[0046] It is preferred that the arrangement of the component surfaceand/or the arrangement of the connecting surface can be adjusted withoutchanging the arrangement of the at least one component. It is alsopreferred that the arrangement of the at least one component can beadjusted without changing the arrangement of the component surfaceand/or the arrangement of the connecting surface.

[0047] It should be understood that the component surface can take anyconvenient form; thus the surface may be a planar surface or anon-planar surface,

[0048] Although components may be arranged in relation to the 3D-modelso as not to extend or so as to only extend partly into the interiorportion of the 3D-model, it is also within embodiments of the presentinvention-that components may be arranged at the interior or innersurface of the inner portion of the 3D-model,

[0049] For 3D-models being shelled according to the present invention,the shell of the 3D-model is preferred to have a predetermined minimumthickness. Within the present invention the shell is also generated by ashelling process being computer-controlled or computer-assisted. Here,the at least partly shelled 3D-model may be obtained from athree-dimensional computer model, 30-model, of at least part of theauditory canal, said 3D-model having an outer shell surface beingparameterised by a number of vertices, which vertices are connected bytriangles, said shelling process comprising:

[0050] offsetting inwardly a copy of each vertex in the outer shellsurface,

[0051] removing the number of copied vertices being closer to the outershell surface than a given minimum shell thickness, and

[0052] creating an inner shell by triangulation of the remaining copiedvertices.

[0053] Within the present invention the inner shell surface or geometryof the 3D-model is also modified in order to improve the strength of thefinished shell, said modification comprising adding extra material tothe inner surface of the shell, while at the same time avoidingcollision between the modified inner shell surface and the arranged at25 least one component. Here, the addition of extra material to theinner shell surface of the 3D-model may be performed using a Booleanoperation, such as a Boolean addition, using a transfer function orusing an outward offset of the vertices representing the surface

[0054] A number of different components may be arranged in relation tothe 3D-model. Such components may for example be selected from a list ofcomponents comprising electronic components, battery devices, outlets tointerior components, tubes, transducers and logos.

[0055] In order to obtain a final 3D-model, further steps may beincluded in the modelling process. Such steps may comprise: arrangementof a ventilation channel at the interior or inner surface of the innerportion of the 3D-model, an optimisation of the visual appearance,and/or placement of a unique identifier at the inner portion of the3D-model.

[0056] According to a further aspect the invention relates to a computerprogram product including a computer readable medium, said computerreadable medium having a computer program stored thereon, said programfor causing computer-assisted modelling of customised earpiecescomprising at least one part being individually matched to an auditorycanal, said program comprising:

[0057] program code for causing a computer to obtain a three-dimensionalcomputer model, 3D-model of at least part of the auditory canal, said3D-model having an outer surface,

[0058] program code for causing a computer to initially arrange at leastone component in relation to the 3D-model,

[0059] program code for causing a computer to initially arrange acutting curve or cutting surface in relation to the outer surface of the3D-model, said cutting curve or surface dividing the 3D-model in anouter portion and an inner portion,

[0060] program code for causing a computer to initially form aconnecting surface connecting the at least one component and the innerportion of the 3D-model, said connecting surface thereby being part ofthe 3D-model,

[0061] program code for causing a computer to perform an evaluation ofthe arrangement of the at least one component, said evaluationcomprising a collision detection of the at least one component inrelation to one or more parts of the 3D-model, and

[0062] program code for causing a computer to adjust the arrangement ofthe at least one component, the arrangement of the cutting curve orsurface, and/or the formation of the connecting surface based on theresult of said evaluation.

[0063] The computer program product is especially adapted for causing acomputer to perform the operations of the method according to the firstaspect of the invention and may further comprise program code forcausing a computer to perform any of the steps of any of the features ofthe method according to the invention.

[0064] The computer program product may be in the physical form of ahard disc, a floppy disc, a magnetic data carrier, a ZIP, a smart card,a CD ROM, or a DVD.

[0065] According to a further aspect the invention relates to a computerdata signal embodied in a signal wave, said computer data signalincluding a computer program, said program for causing computer-assistedmodelling of customised earpieces comprising at least one part beingindividually matched to an auditory canal, said program comprising:

[0066] program code for causing a computer to obtain a three-dimensionalcomputer model, 3D-model, of at least part of the auditory canal, said3D-model having an outer surface,

[0067] program code for causing a computer to initially arrange at leastone component in relation to the 3D-model,

[0068] program code for causing a computer to initially arrange acutting curve or cutting surface in relation to the outer surface of the3D-model; said cutting curve or surface dividing the 3D-model in anouter portion and an inner portion,

[0069] program code for causing a computer to initially form aconnecting surface connecting the at least one component and the innerportion of the 3D-model, said connecting surface thereby being part ofthe 3D-model,

[0070] program code for causing a computer to perform an evaluation ofthe arrangement of the at least one component, said evaluationcomprising a collision detection of the at least one component inrelation to one or more parts of the 3D-model, and

[0071] program code for causing a computer to adjust the arrangement ofthe at least one component, the arrangement of the cutting curve orsurface, and/or the formation of the connecting surface based on theresult of said evaluation.

[0072] The computer data signal is especially adapted for causing acomputer to perform the operations of the method according to the firstaspect of the invention and may further comprise program code forcausing a computer to perform any of the steps of any of the features ofthe method according to the invention.

[0073] According to a further aspect the invention relates to a systemfor computer-assisted modelling of customised earpieces, said systemincluding computer readable memory having one or more computerinstructions stored thereon, said instructions comprising

[0074] instructions operative to cause the computer to obtain athree-dimensional computer model, 3D-model, of at least part of theauditory canal, said 3D-model having an outer surface,

[0075] instructions operative to cause the computer to initially arrangeat least one component in relation to the 3D-model,

[0076] instructions operative to cause the computer to initially arrangea cutting curve or cutting surface in relation to the outer surface ofthe 3D-model said cutting curve or surface dividing the 3D-model in anouter portion and an inner portion,

[0077] instructions operative to cause the computer to initially form aconnecting surface connecting the at least one component and the innerportion of the 3D-model said connecting surface thereby being part ofthe 3D-model,

[0078] instructions operative to cause the computer to perform anevaluation of the arrangement of the at least one component, saidevaluation comprising a collision detection of the at least onecomponent in relation to one or more parts of the 3D-model, and

[0079] instructions operative to cause the computer to adjust thearrangement of the at least one component, the arrangement of thecutting curve or surface, and/or the formation of the connecting surfacebased on the result of said evaluation.

[0080] The system is especially adapted for performing the operations ofthe method according to the first aspect of the invention and mayfurther comprise instructions operative for causing the computer toperform any of the steps of any of the features of the method accordingto the invention.

[0081] Preferably the system according comprises a 3D scanner, acomputer and a computer controllable rapid prototyping machine. Therebyis provided a complete system for scanning, modelling and prototypingcustomised earpieces.

[0082] The rapid prototyping machine may be any rapid prototypingmachine capable of being controlled by a computer. Examples include butare not limited to machines capable of performing 3D milling and/orstereo lithography/SLA and/or solid ground curing and/or selective lasersintering and/or direct shell production casting and/or 3D-printingand/or topographic shell fabrication and/or fused deposition modellingand/or inkjet modelling and/or laminated object manufacturing and/ornano-printing.

[0083] The system may be arranged in different ways. Accordingly, thescanner and/or the prototyping machine may be connected to the computervia a local area network or the scanner and/or the prototyping machinemay be connected to the computer via the internet.

[0084] Consequently the 3D scanner, the computer and the rapidprototyping machine may be placed in the same locality. Alternatively,the computer for modelling may be is placed at a “modelling site”, wheretrained staff can perform the optional manual steps of the modelling.According to this embodiment, scan data can be sent via the internet orvia other data transmission systems to the “modelling site”.

[0085] Similarly, the rapid prototyping machine may be placed at a“rapid prototyping site”, where the very costly machinery can beoperated efficiently and on a 24 hour basis to keep production costslow.

[0086] The 3D scanner is conveniently placed by an audiologist or anotologist, especially when the scanner is a 3D structured light scannerfor scanning the internal contours of the ear canal and/or meatus.

[0087] Preferably the system further comprises a database, wherein scandata are stored. According to an especially preferred embodiment of theinvention, the system comprises a further database, wherein 3D data forcustomised earpieces are stored. These databases can be accessed duringmodelling of the earpieces and are especially useful when the method isperformed on a similarity based approach.

[0088] The data are preferably stored together with informationidentifying the users of the customised earpieces.

[0089] An optional further database, comprises 3D data for componentsfrom different manufacturers. These can also be used for the modellingprocess.

[0090] Further optional hardware includes, but is not limited tospaceball™ tracking device to assist in manual or computer assistedmodelling and stereo glasses to assist in manual inspection of 3Dcomputer screen models.

[0091] According to a further aspect of the present invention there isprovided a method for computer-assisted modelling of customisedearpieces comprising at least one part being individually matched to anauditory canal and/or a meatus, said method comprising the steps of:

[0092] a) obtaining a three-dimensional computer model, 3D-model, of atleast part of the auditory canal, said 3D-model having an outer surface,

[0093] b) initially arranging a at least one component in relation tothe 3D-model,

[0094] c) initially arranging a cutting curve or cutting surface inrelation to the outer surface of the 3D-model, said cutting curve orsurface dividing the 3D-model in an outer portion and an inner portion,

[0095] d) initially forming a closing surface closing the hole partly orcompletely created in the 3D model by the cutting curve/cutting surface,

[0096] e) performing an evaluation of the arrangement of the at leastone component, said evaluation comprising a collision detection of thecomponents in relation to one or more parts of the 3D-model and/or othercomponents, and

[0097] f) adjusting the arrangement of the at least one component, thearrangement of the cutting curve or surface, and/or the formation of theconnecting surface based on the result of said evaluation.

[0098] According to the present aspect of the invention is provided adifferent method for modelling earpieces. If the closing surface is notcompletely closed and if the at least one component is places in thehole, the closing surface fulfils the same function as the connectingsurface according to the first aspect of the invention. Anotherpossibility according to this aspect of the invention is to model an 3Dearpiece with a hole into which the components of the earpiece can beinserted after prototyping. It should be understood that the method ofthe second aspect of the present invention may be combined with any ofthe methods of the first aspect of the invention, wherein the componentsare arranged in relation to a cutting surface.

[0099] This aspect of the invention may also be in the embodiment of acomputer program product or a computer data signal embodied in a signalwave comprising computer program code for performing the method and inthe embodiment of a system including computer readable memory having oneor more instructions stored thereon, the instructions comprisinginstructions operative for causing the system to perform the method.

[0100] According to a further aspect of the present invention there isprovided a method for computer-assisted modelling of customisedearpieces comprising at least one part being individually matched to anauditory canal, said method comprising the steps of:

[0101] obtaining a three-dimensional computer model, 3D-model, of atleast part of the auditory canal, said 3D-model having an outer surface,

[0102] initially arranging at least one component in relation to the3D-model,

[0103] initially arranging a cutting curve or surface in relation to theouter surface of the 3D-model,

[0104] said cutting curve or surface dividing the 30-model in an outerportion and an inner portion,

[0105] said initial arrangement of the cutting curve or surface and thecomponents being performed using a similarity-based approach in whichthe present obtained 3D-model is compared to a number-of stored modelsof previously generated optimised 3D-models, with one of said stored3D-models being selected as the most similar model and the initiallyarrangements of the cutting curve or surface and the components beingset substantially equal to the optimised arrangements of the cuttingcurve or surface and the components of said most similar 3D-model.

[0106] Here, the comparison of the present 3D-models and selection ofthe most similar 3D-model may be computer controlled or computerassisted. Also, the selection of initial arrangement of the cuttingcurve or surface and components may be computer controlled or computerassisted.

[0107] This aspect of the invention may also be in the embodiment of acomputer program product or a computer data signal embodied in a signalwave comprising computer program code for performing the method and inthe embodiment of a system including computer readable memory having oneor more instructions stored thereon, the instructions comprisinginstructions operative for causing the system to perform the method.

[0108] It is preferred that the method of this aspect of the inventionfurther-comprises the step of initially forming a connecting surfaceconnecting the components and the inner portion of the 3D-model, saidconnecting surface thereby being part of the 3D-model.

[0109] The method of the this aspect of the present invention shouldpreferably further comprise the steps of performing a collisiondetection of said arranged components in relation to one or more partsof the 3D-model, and adjusting the arrangement of the at least onecomponent and/or the arrangement of the cutting curve or surface basedon the result of said collision detection. Here, the adjustment of thearrangement of the cutting curve or surface and/or the arrangement ofthe at least one component may be repeated until the collision detectionfulfils a required minimum criterion.

[0110] According to a further aspect the invention relates to a methodfor computer-assisted modelling of customised earpieces comprising atleast one part being individually matched to an auditory canal, saidmethod comprising the steps of:

[0111] obtaining a three-dimensional computer model, 3D-model, of atleast part of the auditory canal, said 3D-model having an outer surface,

[0112] initially arranging a at least one component in relation to the3D-model,

[0113] initially arranging a cutting curve or cutting surface inrelation to the outer surface of the 3D-model, said cutting curve orsurface dividing the 3D-model in an outer portion and an inner portion,

[0114] said initial arrangement of the at least one component and/orcutting curve or surface being performed using a feature-based approach,in which features extracted from the obtained 3D-model are used for thearrangement.

[0115] This aspect of the invention may also be in the embodiment of acomputer program product or a computer data signal embodied in a signalwave comprising computer program code for performing the method and inthe embodiment of a system including computer readable memory having oneor more instructions stored thereon, the instructions comprisinginstructions operative for causing the system to perform the method.

[0116] For the embodiments of the first aspects of the presentinvention, the 3D-model, present 3D-model or previously stored optimised3D-models may have an outer shell surface being parameterised by anumber of vertices, which vertices are connected by triangles. For theembodiments using a similarity-based approach the selection of the mostsimilar 3D-model may comprise:

[0117] extracting a number of features from the obtained or present3D-model,

[0118] comparing said number of extracted features with correspondingstored features of a number of stored previously optimised 3D-models,and

[0119] selecting a number of stored 3D-models as candidates for the mostsimilar 3D-model, said candidates being the stored 3D-models having thecompared features being nearest neighbours, in a feature space, to thefeature points of the present 3D-model.

[0120] The selection process may further comprise:

[0121] registration of the present 3D-model and the selected candidate3D-models,

[0122] selection of the most similar 3D-model as the model of candidate30-models having the smallest between the outer shell surface of saidcandidate 3D-model and the outer shell surface of the present 3D-model.

[0123] It should be understood that the methods of the third aspect ofthe present invention may be combined with any of the methods of thefirst and second aspects of the invention using a similarity basedapproach.

[0124] According to a still further aspect of the present inventionthere is provided a method for shelling a 3D model, said methodcomprising the steps of:

[0125] obtaining a three-dimensional computer model, 3D-model, of atleast part of the auditory canal, said 3D-model having an outer shellsurface being parameterised by a number of vertices, which vertices areconnected by triangles, and

[0126] performing a shelling process to obtain a shelled 3D-model of atleast part of the auditory canal, said shelling process comprising:

[0127] offsetting inwardly a copy of each vertex in the outer shellsurface,

[0128] removing the number of copied vertices being closer to the outershell surface than a given minimum shell thickness, and

[0129] creating an inner shell by triangulation of the remaining copiedvertices.

[0130] According to a further aspect the invention relates to a computerprogram product including a computer readable medium, said computerreadable medium having a computer program stored thereon, said programfor causing computer-assisted shelling of a 3D model, said programcomprising:

[0131] program code for causing a computer to obtain a three-dimensionalcomputer model, 3D model, of at least part of the auditory canal, said3D-model having an outer shell surface being parameterised by a numberof vertices which vertices are connected by triangles, and

[0132] program code for causing a computer to perform a shelling processto obtain a shelled 3D-model of at least part of the auditory canal,said shelling process comprising:

[0133] program code for causing a computer to offset inwardly a copy ofeach vertex in the outer shell surface,

[0134] program code for causing a computer to remove the number ofcopied vertices being closer to the outer shell surface than a givenminimum shell thickness, and

[0135] program code for causing a computer to create an inner shell bytriangulation of the remaining copied vertices.

[0136] According to a still further aspect the invention relates to acomputer data signal embodied in a signal wave, said computer datasignal including a computer program, said program for causingcomputer-assisted shelling of a 3D model, said program comprising:

[0137] program code for causing a computer to obtain a three-dimensionalcomputer model, 3D-model, of at least part of the auditory canal, said3D-model having an outer shell surface being parameterised by a numberof vertices, which vertices are connected by triangles, and

[0138] program code for causing a computer to perform a shelling processto obtain a shelled 3D-model of at least part of the auditory canal,said shelling process comprising:

[0139] program code for causing a computer to offset inwardly a copy ofeach vertex in the outer shell surface,

[0140] program code for causing a computer to remove the number ofcopied vertices being closer to the outer shell surface than a givenminimum shell thickness, and

[0141] program code for causing a computer to create an inner shell bytriangulation of the remaining copied vertices.

[0142] Furthermore, the invention relates to a system for computerassisted shelling of a 3D-model said system including computer readablememory having one or more computer instructions, stored thereon, saidinstructions comprising:

[0143] instructions operative to cause the computer to obtain athree-dimensional computer model, 3D-model, of at least part of theauditory canal, said 3D-model having an outer shell surface beingparameterised by a number of vertices, which vertices are connected bytriangles, and

[0144] instructions operative to cause the computer to perform ashelling process to obtain a shelled 3D-Model of at least part of theauditory canal, said shelling process comprising:

[0145] instructions operative to cause the computer to offset inwardly acopy of each vertex in the outer shell surface.

[0146] instructions operative to cause the computer to remove the numberof copied vertices being closer to the outer shell surface than a givenminimum shell thickness, and

[0147] instructions operative to cause the computer to create an innershell by triangulation of the remaining copied vertices.

[0148] Also here it should be understood that the shelling methodaccording to the last aspects of the present invention may be used inany of the methods of the first aspects of the present invention inorder to obtain a shelled 3D-model.

[0149] The shelling algorithm according to the present invention makesit possible to perform shelling in a rapid and simple way.

BRIEF DESCRIPTION OF THE DRAWINGS

[0150] The invention will now be explained in more detail in conjunctionwith the enclosed drawings on the basis of various example embodimentsin which:

[0151]FIG. 1 shows an In-The-Ear Hearing Aid;

[0152]FIG. 2 shows a Completely-In-Canal Hearing Aid;

[0153]FIG. 3 shows a wireless In-The-Ear Communication device;

[0154]FIG. 4 shows an in-The-Ear Adaptive earpiece;

[0155]FIG. 5 gives an overview of a full process and the hardwarecomponents;

[0156]FIG. 6 shows two original 3D models of two impressions;

[0157]FIG. 7 gives an illustration of triangular based representationwith the same 3D model visualized as shaded and as wire frame;

[0158]FIG. 8 shows a simplified example of a modelling process and theinvolved modelling operations;

[0159]FIG. 9 shows a simplified example of a modelling process and thinvolved modelling operations;

[0160]FIG. 10 shows a simplified example of the modelling processillustrated by images of the evolution of the model;

[0161]FIG. 11 illustrates a removal of a defects related to a thread,which are used to remove the impression from the ear;

[0162]FIG. 12 illustrates two simple virtual reference ear modelscreated from the corresponding models shown in FIG. 6;

[0163]FIG. 13 shows a 3D model before and after cutting and closing by asimple planar surface defined by control points and a surfaceorientation;

[0164]FIG. 14 Illustrates intersections between one model triangle andthe surface triangles in a triangular-based representation of a 3Dmodel;

[0165]FIG. 15 shows the cutting of the triangles between two pointessampled on a curve and projected onto the 3D model. The cutting isperformed by a local cutting plane;

[0166]FIG. 16 Illustrates cutting and closing of the top of a shelledmodel with a planar surface with thickness equal to the shell thickness;

[0167]FIG. 17 show a flow chart for the loop used for a manual approachfor the component placement, cutting and filleting/lofting of thevisible part of the surface;

[0168]FIG. 18 illustrates a manual placement of the component surfaceand the components—in this case an integrated battery and electronics;

[0169]FIG. 19 shows an example of collision between component and shellsurface;

[0170]FIG. 20 illustrates a spatial division of the space into cubes;

[0171]FIG. 21 contains a flow chart for the loop used by a rule-basedapproach for the optimal component placement, cutting andfilleting/lofting of the visible part of the surface;

[0172]FIG. 22 shows a cutting by a closed curve on the surface. Thecurve is defined by the number of control points;

[0173]FIG. 23 shows the first step in the illustrated loft operation,which is to determine the correspondence between the vertices at the twoboundaries;

[0174]FIG. 24 illustrates the result of lofting the model and componentsurface in FIG. 22 visualised alone and in the reference ear;

[0175]FIG. 25 illustrates the result of a lofted surface when theadditional control points between the corresponding vertices have beenmoved backward along v_(c1) and v_(c2) until they are located behind thesurface of the reference ear;

[0176]FIG. 26 illustrates the result of a shelling;

[0177]FIG. 27 is a flow chart of a shelling algorithm;

[0178]FIG. 28 illustrates the proper offset of each vertex to ensureminimum shell thickness when using a vertex representation of a 3Dmodel;

[0179]FIG. 29 illustrates an IN-THE-EAR earpiece with an area in softermaterial;

[0180]FIG. 30 shows a manual cutting with a planar surface at the canalpart of the surface followed by a filleting/lofting;

[0181]FIG. 31 illustrates a placement of components on the canal part ofthe surface. The components correspond to a sound outlet, the transducerand the tube, which connect the transducer and the outlet;

[0182]FIG. 32 is a flow chart for the loop used for the manual approachfor cutting and component placement on the canal part of the surface;

[0183]FIG. 33 illustrates a manual creation of a ventilation channel;

[0184]FIG. 34 shows an IN-THE-EAR earpiece with a double ventilationchannel;

[0185]FIG. 35 shows an IN-THE-EAR earpiece with a feedback reductionchamber;

[0186]FIG. 36 shows an IN-THE-EAR Hearing Aid with variable shellthickness and holding spikes;

[0187]FIG. 37 illustrates the creation of a lock for the electronics andbattery component;

[0188]FIG. 38 illustrates the creation of room for the faceplate with aplanar backside by performing a cut with the surface corresponding tothe backside of the faceplate;

[0189]FIG. 39 shows an example of identification placed on the inside ofthe shell or as a detachable tag;

[0190]FIG. 40 illustrates Boolean functions on two 3D models, A and B;

[0191]FIG. 41 illustrates a difference map showing the penetration ofthe reference ear by a final earpiece;

1. DETAILED DESCRIPTION OF THE INVENTION

[0192] 1.1 General Definitions

[0193] 3D: A General Abbreviation for Three-Dimensional.

[0194] 3D modelling operations: A number of different operations thatalter the geometry of the original 3D model. These operations are usedto change the outer and inner geometry of the earpiece. The 3D modellingoperations are also'used to make an optimal placement of the innercomponents of the apparatus.

[0195] 3D model: A geometric representation of an object. This caneither be an object of unique and complex geometry obtained by using athree dimensional scanning device or an object parametrically generatedusing a traditional CAD system or another 3D modelling software program.Different types of representations of 3D models exist. In one of themost common representation the 3D model is parameterised by a number ofvertices, which are connected by triangles, see FIG. 7.

[0196] Original 3D model: The 3D scan of the meatus and/or auditorycanal before any 3D modelling operations have been performed on themodel. This model is often generated by scanning an impression of theauditory canal using an optical, acoustic, mechanical, or other 3Dscanning apparatus. The original 3D model can also be obtained by usingan intra canal 3D scanning device.

[0197] Present 3D model: A 3D model that exists as a temporary step inthe total 3D modelling sequence. The present 3D model can therefore beany representation of the 3D model between the Original 3D model and theFinal 3D model

[0198] Final 3D model: A 30 model of the final earpiece. The final 3Dmodel usually includes the geometry of the arranged components. Otheruseful geometric alterations of the original 3D model are also coveredby this definition.

[0199] Component: A general term used for any type of component, featureor unit used with the device. Examples of components are ventilationchannel, amplifier, Microphone, vibration pick-up, microchip,transducer, wireless communication/identification devices, positionsensors such as GPS, loudspeaker, tubes, battery, printed circuits,faceplate, surface patches, inlets, outlets, wires, conductors, volumecontrols, nail grip, extraction cord, tele coil, locking means,interface modules, identification and logo.

[0200]30

[0201] Cutting tool: A tool such as an arbitrary curve or surface usedto divide the model into two portions, where one of the portions are cutaway, see e.g. FIG. 13 or FIG. 22.

[0202] Earpiece: The earpiece includes housings for hearing aids,wireless or connected communication devices (headsets, mobile phones,personal agents), loud speakers, tinnitus masking devices, devicesrecording vibrations in the skull and transforming these into audiosignals, voice recognition devices, earplugs, noise blockers withselective frequencies or sound levels, Man Machine Interface (MMI)products that enable clear communication even in the easiestenvironments, or products related to wireless Internet applications.

[0203] Canal part of the surface: The canal part of the surfacecorresponds to the part of the model surface, which is inside theauditory canal, see FIG. 6 Inner shell surface: The surfacecorresponding to the internal part of the shell 2603, see FIG. 26.

[0204] Outer shell surface: The surface corresponding to the outer partof the shell 2604, see FIG. 26.

[0205] Visible part of the surface: The visible part of the surface isdefined as part of the model surface, which is partly or fully visiblewhen the earpiece is inserted in the ear.

[0206] Triangulation: The process of connecting vertices by triangles.

[0207] Vertex: A point in the 3D space. The vertices are connected byedges forming simple polygons, e.g. triangles, see FIG. 7.

[0208] Connecting surface: A connecting surface (FIG. 24, 2401) is agenerated surface connecting a component with the inner portion of the3D model. The connecting surface may also be defined as a generatedsurface connecting a component surface with the inner portion of the 3Dmodel. In the finished product the connecting surface may either beprinted/produced together with the inner portion of the customisedearpiece or it may be formed by milling it in a faceplate part (FIG. 38,3803) in which a component can be inserted.

[0209] Cutting curve/surface; A cutting curve/cutting surface is acurve/surface defined by the user or the computer and dividing the 3Dmodel into a outer and inner portion. See FIG. 13; 1303 and FIG. 38,3801 for examples of a cutting surface and FIG. 22, 2203 for an exampleof a cutting curve,

[0210] Outer portion/Inner portion: The terms are used to designate thetwo'parts of the model that arise as a result of cutting of the 3D modelwith a cutting curve or surface, The inner portion is the portion of themodel; which is closest to the meatus of the user. FIG. 22 shows anexample of a 3D model divided into an inner portion 2206 and outerportion 2207. The outer portion of the 3D model may form a virtual ear.

[0211] Component surface: The components are usually arranged inrelation to a related component surface, which is then connected withthe rest of the shell preferably by a cutting or loft operation. Analternative strategy is to create the component surface directly fromthe-arranged components. The component surface is not necessarily anintegrated part of the final 3D model. It could be a separate cover orfaceplate, which is assembled with the shell later in the productionprocess. FIG. 18 illustrates the arrangement of the component consistingof electronics and battery 1801 and the related component surface 1802.

[0212] 1-2 General Specification of the System

[0213]FIG. 1 schematically shows an In-The-Ear hearing aid, whichtypically consists of a shell or otoplasty 101 closed by a face or coverplate 102, a control switch 103, a sound inlet 104, a microphone 105, anelectronic amplifier 106, a feedback control device 107, a replaceablebattery 108, a battery compartment 1069, an transducer 110, a soundoutlet 111 and a ventilation channel 112. FIG. 2 shows the smallerCompletely-In-Canal hearing aid, which consist of the same componentswith an additional removal handle 201. Another example of a device wornin the ear is the wireless communication device in FIG. 3, whichtypically consists of a large number of similar components as thehearing aids and an additional microphone with vibration pickup 301 anda wireless transmitter 302. Finally is shown a simple adaptive earpiecein FIG. 4, which typically consists of a shell 101, a ventilationchannel 112 and a sound tube 401.

[0214]FIG. 5 shows an overview of the full process for manufacturing ofcustomised earpieces and the involved hardware. The hardware comprises a3D scanning device 501, a computer 502 and rapid prototype machine 503.Additional hardware devices are a database server 504, a spaceballtracking device 505 and 3D stereo glasses 506. The process consists ofthree main steps: 3D data capturing, 3D modelling and 3D manufacturing.As indicated in FIG. 5 3D data capturing. 3D modelling and 3Dmanufacturing can be performed at different physical locations tooptimise cost and quality. Distribution is easily implemented, since theinvention allows the original and final model to be transferred over theInternet. In general the invention is mainly focused on the modellingpart. The individual operations will be described in details below.

[0215] The optimal output of the system varies from application toapplication and must initially be specified by human interaction orintelligent suggestions from a computer. In the case of hearing aids,ear worn communication devices and other mechanical or electricaldevices worn in the ear, the goal is usually to optimise the size, thevisual appearance, the acoustic properties and the placement of thecomponents inside the earpiece. A perfect fit to the users ear is alwayswished for.

[0216] The system is implemented in two steps: initially the systemrequires input from an operator, and after a learning/training periodthe system may become fully or almost fully automated and may handle allsteps with no or very little operator interaction. Manufacturers may getthe system after the training has been performed to the specificapplication and may thus need virtually no human interaction to producethe desired result.

[0217] Often a quality assuring person or the user will judge the finalearpiece and apparatus before it is physically produced by the system.

[0218] 1.3 3D Data Capturing

[0219] The first step in the production process is to capture a 3Ddigital model of the impression or directly of the auditory canal usinga 3D scanning device. Two examples of original 3D models 601, 602 areillustrated in FIG. 6. Note that the medium size model 601 onlycorresponds to the part of the large model 602, which is marked by abox. Note also the definition of the canal part of the surface 603, thevisible part 604 of the surface and which part that corresponds to theauditory canal 605. Different types of representations of 3D modelsexist. FIG. 7 illustrates the very common triangular-basedrepresentation, where the 3D model surface 701 is parameterised by anumber of vertices, which are connected by triangles 702.

[0220] The preferred embodiment of a 3D scanning apparatus for the givenapplication is a non-contact system. The 3D scanning device is typicallybased on the projection of one or more sheets of light or another knownpattern of light onto an impression of the ear. The source ofillumination is typically a low-power laser in the visibly lightspectrum. Non-visible wavelengths can be used but this requires a sensorthat can capture in the given spectrum. Non-contact 3D scanning of anear impression can also be done using ultrasound, magnetic resonance orcomputer tomography (CT) scanners.

[0221] 3D optical scanners capture series of profiles or another knownpattern of light from the illuminated auditory canal-impression. Mostoften the light pattern on the object is one or more distinct lines.These profile-lines are digitised in real time by an optical sensor.When the ear impression or the optics are moved, other profiles becomeavailable. With continuous motion, the 3D scanner automaticallydigitises object profiles from multiple views. Some 3D scanners candigitise an object's profile as dense as every 0.01 mm, which results ina highly detailed digital representation of the object being scanned.The ear impressions are preferably placed on fixtures and automaticallyfed to the scanner. One example of a suitable scanning apparatus andmethod is disclosed in PCT/DK01/00564 (3Shape). 3D scanners that do notrequire an impression of the ear can also be used in the presentinvention. These are using a probe that is directly inserted into theear. The preferred probes do not touch the ear-canal during the scanningprocess. The preferred probes either work by the use of ultrasound (WO00/34739 Fagan et al.) or preferably the projection of a knownlight-pattern onto the auditory canal (PCT/DK01/00561, 3Shape).

[0222] The 3D scanner may also capture the texture of the impression.Capturing the texture can facilitate that text and marks can be drawndirectly on the impression by the user or audiologist and read by thesystem or operator during modelling. This enables e.g. the user to markareas, which causes pain or special visual requirements. Marks and textcan be extracted directly from the texture images using classic imageprocessing operations such as adaptive threshold or edge detection. Theextracted information can then be projected onto the model andprocessed, e.g. areas marked for causing pain can be projected onto themodel and material can be removed in the corresponding area.

[0223] Other examples of information that can be marked on theimpression include: marking of an arrangement of a cuttingcurve/surface; marking of an arrangement of the vent or exits forvent(s); marking of identification tag (name or identity of the user oraudiologist); marking of soft and hard areas of the auditory canal;marking of an arrangement of components; marking of the arrangement offeatures of the outer ear. It is to be understood that when severaldifferent features are marked, these can be marked in different colour,which can be distinguished by the texture scan. Text writing can berecognised by OCR during the modelling.

[0224] The captured 3D model may be saved in a database available in alocal area network or over the Internet.

[0225] 1.4 3D Modelling

[0226]FIG. 10 shows a simplified version of the modelling processillustrated with the evolution of the present model during themodelling. FIG. 8 and FIG. 9 show two examples of the operations, whichmay be involved in the modelling process. The modelling operations801-816 and 901-916 performed to create the final 3D model given theoriginal 3D model are described in details below. Three examples areincluded to show that the individual steps are not necessarily performedin the order described but can be performed in a number of differentsequences with an equally satisfying result Different orders havedifferent advantages. The system can also try the steps in a randomisedorder to iterate towards the best solution. Note that the modellingprocess usually is an iterative process, where different properties e.g.the positions of components or the path of the ventilation channel arechanged a number of times until a satisfying result is obtained.

[0227] The automation of the modelling software may be done usingtwo-approaches that can either complement each other or worksingle-handed; During the automated steps the system can, at any time,request the input from an operator or switch to the other automationapproach

[0228] Similarity-Based Approach

[0229] One approach used to automate the system is to extract thenecessary modelling information from a database. This database containsoriginal 3D models of the auditory meatus and canal from differentpersons. For each original 3D model all operations and settings used tocreate an optimal final 3D model are recorded. When a new model needs tobe processed the most similar model is extracted from the database.Given the most similar 3D model, the computer software repeats the samesequence of operations that were performed on the extracted model inorder to obtain the desired final 3D model. For successful use of theoperations a registration, i.e. an alignment, of the new model to theextracted model may, be performed. Details on the extraction of the mostsimilar model are given in section 1.4.18. Some operations and settingsmay need to be adjusted to compensate for different position,orientation and size between the two models.

[0230] Most ear canals of a person are to a large extent a mirroredversion of the opposite canal. A variant of the similarity-basedapproach is to apply the operations and settings for an already modelledear to the opposite ear, i.e. apply the used operations and settings forthe left ear to the right ear of the same person. The only difference isthat the first ear and the applied operations and settings need to bemirrored, before it can be applied. The mirroring of the ear can beperformed by C mirroring the vertices in an arbitrary plane since theactual plane only changes orientation and position of the mirroredmodel. Likewise the operations and settings need to be mirrored in thesame plane.

[0231] Rule-Based Approach

[0232] The other approach incorporated in the system is to define a setof mathematical rules and implement these into algorithms that optimisethe results of the individual steps in the modelling process. Theoptimal result of the individual operations takes into consideration theoverall use of the final apparatus. The purpose varies with theapplication of the device.

[0233] 1.4.1 Closing of Holes

[0234] Many scanning devices create original models with holes in thesurface, i.e. the model surface is not closed. Models with uniclosedsurfaces cannot exist from a physical point of view, so the holes needto be closed, due to e.g. occlusion effects. In a triangular-basedrepresentation holes are determined by counting the number of trianglesat each edge. The edge corresponds to a boundary if only one triangle ispresent on the edge. Boundary edges always create loops defining thehole in the surface.

[0235] Triangulation of Hole

[0236] In the case of triangular-based representation the followingapproach is preferably applied to close each hole. If the hole is small,e.g. defined by the boundary length, a triangulation is performed bydirectly connecting the vertices on the boundary by non-intersectingtriangles. The triangulation is performed using a standard 3Dtriangulation method such as proposed by Hoppe et al. in “SurfaceReconstruction from unorganised points”, Computer Graphics, 26(2), 1992,pp. 71-78.

[0237] Preferably the first step in closing large holes is to perform afit of a parametric surface to the vertices on the boundary of the holeand the vertices in its neighbourhood. The parametric surface shouldpreferably be smooth such as a 2^(nd), 3^(rd) or lower order surface, aNURBS surface or another type of spline surface. The neighbourhood maybe manually marked or defined as the vertices in a certain distance fromthe boundary. To triangulate large holes new vertices are sampled on thefitted surface. These sampled vertices are then connected by triangles.One method for performing this operation is described in 1.4.7. Thetriangulated hole can be smoothed (see section 1.4.12) to improve visualappearance.

[0238] 1.4.2 Removal of Defects

[0239] A number of defects and artefacts are often present in theoriginal impression and hence in the original 3D model These defectsoriginate from a number of different sources such as the impressioncreation, scars, tissue or hair in the ear, the thread used to removethe impression from the ear or small scratches and cuts from thehandling. FIG. 11 shows defects 1105 originating from the thread. Otherartefacts, such as bents on the ear channel, also need to be removed toobtain an earpiece, which is pleasant to use.

[0240] Manual-Based Approach

[0241] To remove defects the area containing the defects may be markedusing a proper selection tool. The choice of selection depends on theshape of the defect. A number of selection tools can be used based onpoint selections, rectangular selection, circle selections, brushselections, semi-coplanar selection, flood selections, edge selections,rim selections and selections along a curve defined by a number ofcontrol points.

[0242] In the case of the removal of the thread defect a curve-basedselection 1106 is usually preferable and the thread is marked by placinga number of points along the defect. To remove the defect the markedtriangles are removed and the hole 1007 is closed following section1.4.1. Figure it shows the input model 1101, the selection of the defect1102, the hole to close 1103 and the model 1104 with the defect removed.

[0243] Other defects or artefacts are removed in a similar fashion,whereby the defect or artefact is marked and removed followed by aclosing of the hole (see section 1.4.1).

[0244] Rule-Based Approach

[0245] The ear surface may be characterized by a soft and smoothsurface. In contrast, defects may be characterized by sudden changes inthe surfaces, which can be viewed as holes, valleys, peaks or ridges inthe surface. These differences can be applied to detect defects.

[0246] In practice the local curvature can be calculated in each vertex.Areas containing defects are characterized by a high local variation incurvature. The local variation of the curvature in a vertex iscalculated as the variance of the curvature in the vertices in theneighbourhood, e.g. first order neighbourhood. If the local curvaturevariation exceeds a predefined threshold a defect is assumed to bepresent The rest of the defect is traced by recursively including all,neighbouring vertices with a local curvature variation above the definedthreshold. When the full defect has been traced, the included verticesand their corresponding triangles are removed and the hole is closed inthe same manner as described in the manual approach.

[0247] 1.4.3 Creation of Virtual Reference Ear

[0248] A powerful tool for creation of visually appealing earpieces isto generate a virtual reference ear model. A simple virtual referenceear model is illustrated in FIG. 12. Given a 3D ear model the presentand final appearance of the earpiece can be visualized and the operatorand user obtains a improved imagination of the effect of changingdifferent properties, e.g. shape, size, colour, texture or components.The virtual reference ear also plays an important role in the automatedcutting and placement of components. As a part of the creation of thevirtual ear a coordinate system may also be inserted. The XY-plane inthe coordinates system may be defined along the cheek with the Y-axisparallel with the body. The Z-axis should point into the ear cannel.

[0249] Manual Approach

[0250] A simple virtual reference ear may be obtained by cutting theoriginal model by a single surface such as a plane. Detaileddescriptions of the cutting tools are found in section 1.4.4. The earmodel in FIG. 12 is created by a planar cut of the model in FIG. 6. Toobtain the most realistic impression of an ear the cut may be performedby a surface, which is parallel with the cheek. In the case of manualinteraction the operator interactively defines the cutting surface by anumber of control points on the surface of the original model. Thenumber of control points required depends on the number of freeparameters in the surface. In the case of a plane three points arerequired. Usually the XY-plane in the coordinate system is determineddirectly from the surface. However, two extra points need to be selectedto determine the X-axis and the origo/Z-axis.

[0251] Similarity-Based Approach

[0252] In an automated scheme the cutting surface can be obtained as thesurface applied to the most similar model, which has been extracted fromthe database. The coordinate system is determined in a similar way.

[0253] Rule-Based Approach

[0254] An alternative automated strategy is to extract features,primarily lower order moments. These features are then fed to a neuralnetwork or another type of parametric or non-parametric model, whichoutputs the most likely plane. Such type of approach requires a trainingset, which can be applied to train the neural network. The coordinatesystem is determined in a similar way, but with a separate neuralnetwork.

[0255] An ear model only created from the original 3D model is limitedto the size of this model. A larger model of the full ear or ideally thefull head is desirable for optimal visualization of the visualappearance of the apparatus. Until full and precise 3D models of thehuman head become easily accessible, an ear or head model, which islocally similar to the original model (a so-called dummy head), can beextracted from a database. The extracted model can be merged with theoriginal model and an improved visualization can be obtained. Anotheroption is that a device, which captures the model directly without theuse of impression, may capture the full geometry and texture of the earand/or the head simultaneously.

[0256] 1.4.4 Cutting

[0257] One of the first steps in the modification of the original modelis usually to perform one or more cuts. FIG. 13 shows a model before1301 and after 1302 a cut with a single planar surface 1303 controlledby three control points 1304. The surface orientation 1305 defines whatpart of the model to remove. Finally the hole generated by the cut isclosed by the surface.

[0258] Cutting by a Single-Surface

[0259] Given an arbitrary surface, f(x, y, z)=0, the cutting isperformed by removing all parts of the present model, which areabove/outside this surface, f(x, y, z)>0. To actually perform the cut,all intersections between the model and the surfaces -need to bedetermined and a cut is performed along these intersections.

[0260] In a triangle-based representation a triangular version of thesurface is assumed to be present. The first step is to remove thetriangles with all vertices above the surface. The next step is todetermine the intersecting triangles in the two models, see FIG. 14. Foreach intersecting triangle 1401 in the model the points corresponding tothe intersections 1402 between the edges of this triangle and thesurface triangles 1403 are determined. The possible intersection betweenan edge and the triangle may be determined using Badouel's algorithm(Badouel, D. “An efficient Ray-Polygon intersection”, Graphic Gems, pp.390-393, 1990). Likewise, the intersection points 1404 between thistriangle and the edges of the surface triangles are determined. Togetherwith the vertices 1405 of this triangle, which are below the surface,these intersection points form a closed loop of points. By atriangulation of this loop the proper boundary of the surface cut iscreated for this particular triangle. All the points/vertices in theloop lie in the plane of the triangles which limits the triangulation totwo dimensions. Applying a standard 2D triangulation algorithm such asDelauney triangulation closes the hole. However, Delauney triangulationproduces a triangulation of the convex hole, so'the triangles outsidethe loop need to be removed (or never created).

[0261] Repeating this procedure for each intersecting triangle in themodel creates an output model, which has been cut by a surface. Notethat all triangles with all vertices below/inside the surface are leftuntouched. Refer to section 1.4.5 for details on how to reduce thenumber of triangle intersection tests by a subdivision of the space intocubes.

[0262] Cutting by a Curve on the Surface

[0263] As an alternative to cutting by surfaces the cutting can beperformed by a curve. FIG. 22 shows the model before 2201 and after 2202cutting by a spline curve 2203 defined on the surface of the model. Thecurve 2203 is defined by a number of control points 2204, which alwayslie on the surface of the model. The control points and hence the curvecan be manually adjusted by the operator. The orientation of the curvedetermines what part of, the model to remove, i.e. the part of the modelthat is inside the curve is removed. The curve may also be controlled byother means, than control points.

[0264] To actually perform the cutting an ordered number of points aresampled along the curve. The individual points are then projected ontothe 3D model e.g. using the triangle normal in the previous projectedpoint. The normal in the first point is known from the first controlpoint. Given these projected points, p₁, . . . , p_(n) 1501 on the 3Dmodel (see FIG. 15) the cutting is performed by cutting the individualtriangles between p_(i) and p_(i+1), 1501 by a local plane cut 1502. Thecutting is performed by traversing the intersection points 1503 betweenthe triangle edges and the local cutting plane between p_(i) andp_(i+1). Following the previous section a triangulation is performed ofeach loop consisting of the intersection points in an intersectedtriangle and the triangle vertices 1504 below the cutting plane. Thelocal cutting plane is defined by the point pi and the cross product ofvector from p_(i) to p_(i+1), and the average triangle normals of thetriangles, which p_(i) and P_(i+1), is projected onto. The result ofcuffing by a curve is illustrated in FIG. 22.

[0265] Cuffing by a Single Surface and Closing the Hole

[0266] Usually models with closed surfaces are required; so the holecreated by the surface cutting needs to be closed by the surface, i.e.the surface need to be cut along the intersections with the model andcombined with the model The procedure is equivalent to the one appliedwhen the model is cut by a surface. The only difference is that theinterpretation of surface and model is swapped. In this case the loopsto be triangulated are created for all intersecting triangles in thesurface. Finally merging the pair of intersection points combines thesurface and model, which has been cut, to form the output model. Notethat there exists a one-to-one correspondence between all intersectionpoints in the model and surface, which has been cut. An example ofsurface cutting and closing is shown in FIG. 13.

[0267] Cutting by a Surface with Thickness and Closing the Hole

[0268] In the case of a model with a shell thickness the cutting surfaceneeds to have a thickness if the final shell thickness should not beviolated. A shelled model is shown in FIG. 26. Refer to section 1.4.9for details on shelling. Cutting by a surface with thickness and globalorientation solves the problem with final shell thickness. FIG. 16 showsa model before 1601 and after 1602 cutting by a surface 1603 withthickness. The global orientation of the surface determines what part ofthe model to remove.

[0269] Basically a surface with thickness comprises two non-intersectingindependent single surfaces with opposite orientation and a constant orvarying distance. The orientation of one of the single surfaces isequivalent to the global orientation. This single surface is defined asthe outer single surface and the other as the inner single surface.Parts of the outer single surface correspond to, parts of the outershell surface after the cutting, hence the name.

[0270] In practice the cutting of a shelled model by a surface withthickness may be performed as two independent cuts by the two singlesurfaces. The outer shell surface of th shelled model may be cut andclosed by the outer single surface using the approach described in theprevious section In a similar way the inner shell of the shelled modelmay be cut and closed by the inner single surface, see FIG. 16.

[0271] 1.4.5 Component Placement on the Visible Part of the Surface

[0272] A very important operation for the visual appearance of the finalearpiece is component placement on the visible part of the surface. Thevisible part of the surface is defined as the part of the surface, whichis partly or fully visible, when the earpiece is inserted in the ear.The term components is not limited to traditional components such aselectronics, buttons or battery devices, but can describe any type ofunits, functions or features of the earpiece, e.g. logo, surface patchesor outlets connected to interior components. The placement Is restrictedby a number of factors such as collision between components and otherparts of the model (e.g. shell, ear and other components), room forother components (e.g. ventilation channel, amplifier, microphone,vibration pick-up, microchip, battery, and printed circuits), the anglesof the components in the shell and the angles of the components withrespect to the ear/head. The components are usually arranged in relationto a related component surface, which is then connected with the rest ofthe shell preferably by a cutting or loft operation. An alternativestrategy is to create the component surface directly from the arrangedcomponents. The component surface is not necessarily an integrated partof the final 3D model. It could be a separate cover or faceplate, whichis assembled with the shell later in the production process.

[0273]FIG. 18 illustrates the arrangement of the component consisting ofelectronics and battery 1801 and the related component surface 1802.

[0274] Manual Approach

[0275] The flow chart of the manual approach for component placement andthe closely related cutting and filleting/lofting operations isillustrated in FIG. 17. Note that this flow chart illustrates the orderof the operations used in FIG. 8, but many different orders of theoperations could be applied; see e.g. FIG. 9 or FIG. 10. It is assumedthat the relevant component surface and components such as amplifier,microphone, vibration pick-up, volume control, microchip, battery andprinted circuits, have been selected from the component database.Usually simplified CAD models of the components are applied to reducethe computation time. Depending on the type of component surface, thesurface may also be an imported CAD model, e.g. a faceplate.

[0276] The first step in the manual component placement is usually theplacement of the related component surface 1802 with respect to the 3Dmodel. However the component surface can also be created directly fromthe arranged components. The selected components 1802 are then placed inrelation to the 3D model and component surface by a manual arrangementof the component in the three dimensional space. The manual arrangementof the component surface and the components is usually an iterativeprocess, where the position and orientation of the surface andcomponents are alternately adjusted until an acceptable arrangement 1705is obtained. The present state of the model is visualised in the virtualear (see section 1.4.3) to improve the evaluation of the visualappearance. The visualisation of the ear and the shell can be madetransparent to further facilitate the placement. Note that the parts ofthe components can be below, inside and above the component surfacedepending on the configuration.

[0277] Independent manual placement of component surface and thecomponents is a cumbersome and error prone task. Two tools may improvethe performance of this task significantly. The first tool is to placeand lock the components in relation to the component surface. When theoperator adjusts the component surface the components keep the relativeposition to the surface, but change the position with respect to the 3Dmodel. The position of component and component surface may be temporallyunlocked and the relative position of the components adjusted. In thisit is often an advantage to restrict the component to stay on thesurface.

[0278] The second tool is collision detection 1704, where a test isperformed for collisions between'the components and the relevant partsof the model. FIG. 19 illustrates the collisions 1903 between shellsurface 1901 and the component 1902. Typically the collision detectionis performed with respect to the virtual ear, other components and thepart of the present shell, which has not been removed by the cutting.One approach, to collision detection is to perform a brute force testfor intersections between the surface of the model and the componentmodel. In a triangular-based representation the triangles in one modelneed-to be tested for intersections with the triangles in the othermodel. An exhaustive intersection test between all triangles in the twomodels is very computational expensive. Note that real time collisiondetection is almost mandatory, if the tool should be attractive. Toreduce the computation time and facilitate real time collision a spatialsubdivision of the 3D space into cubes (Fujimoto et al., “Arts:Accelerated ray-tracing system”, IEEE Computer Graphics andApplications, 6(4), pp.16-14, 1986) is performed, see FIG. 20. Each cubeholds a list of all the triangles, which have parts inside it.

[0279] Assume that the cube structure has been created for a model. Ifan intersection test needs to be performed between a new triangle andthis model, only intersection tests between the new triangle and thetriangles, which correspond to the cubes with parts of the new triangleinside, need to be performed. This method can be applied to perform avery fast test of all the triangles in one model with all relevanttriangles in another model. Hence the full intersection test between thetwo models is performed. Based on the collision detection thepenetration of one model into the other is determined. The 3D model usedfor collision detection may be an offset version of the originalcomponent to facilitate a minimum distance is not violated. The offsetdistance usually corresponds directly to the minimum distance.

[0280] Hierarchical collision detection may also be used to obtain lowcomputation times, e.g. by the use of bounding volumes. Preferably thebounding volume should be spheres, axis-aligned bounding boxes, orientedbounding boxes, k-DOPs (discrete orientated polytopes), pie slices orspherical shells.

[0281] An alternative strategy to collision detection is to measure thelocal or global distance from the component surface to the relevantparts of the model. This type of collision detection has a large degreeof freedom, since collision also is detected if the components violate aminimum distance to the relevant parts of the model. This is veryrelevant in the case of required collision detection with respect to theinner shell surface, before the surface is actually created.

[0282] In the case where there is not enough space for the componentsthe shell may be modified in the collision regions to make more room.One way of doing this is to remove material from the shell using aBoolean function, such as subtracting the colliding part of thecomponent from the shell, provided that the component does not penetratethe shell. Another option is to use an iterative offset, which Isrepeated until room enough has been created for the component—again withthe constraint that the component should not penetrate the shell.

[0283] Refer to section 1.4.17 for details on how to add and removematerial. Modifying the shell outwardly will make the final modelintersect with the ear. However this may be a minor problem for limitedmodifications, especially if these are performed in the soft parts ofthe ear.

[0284] Similarity-Based Approach

[0285] Extracting the most similar model and applying the same positionand orientation of the component and the related component surface canautomate the placement of the surface and the components. The collisiondetection presented above can be applied to ensure that no collisionsare present. If collisions exist one of the other approaches can beapplied.

[0286] Rule-Based Approach

[0287] An alternative strategy for the automated placement of componentsis to apply an object function, f(v), which expresses the quality of theplacement, v, of the components (and the closely related componentsurface, cutting and filleting/lofting 20′ operations) The flow chart ofthis approach is shown in FIG. 21. The optimal placement, v*, of thecomponent surface and components can then be obtained by determining theplacement, which optimises the criterion, f(v*)≦f(v) Note that theparameters, v, in FIG. 21 usually also contains the free parametersrelated to the cutting and filleting/lofting operations. Theoptimisation can be constrained by a number of factors such as collisionbetween components and shell room for other components and features(e.g. ventilation channel, amplifier, microphone, vibration pick-up,microchip, battery, and printed circuits), the angle of the component inthe shell and the angle of the component with respect to the ear/head.The, constraints can either be incorporated as hard or soft constraints,where a penalty function is incorporated into the objective function. Inpractice soft constraints can act as hard constraints if a very highpenalty is assigned for violation of the constraint, e.g. a collision.

[0288] The object function, f(v), may consist of a weighted sum of theterms related to the soft constraints and a number of other terms whichexpress the quality of the earpiece. Preferably these terms are thevolume of the shell, the outer shell surface area, the visible shellsurface area, the length of intersection between the reference ear andthe cutting surface, the area of the cutting surface after the cut, themaximal penetration of the reference ear by a component, the average ofthe penetration and the acoustic properties. As seen in FIG. 21 theobject function is usually evaluated after the component placement,cutting and filleting/lofting operations have been performed. Howeverf(v) could be evaluated at any time after the parts to evaluate have arepresent in the model. The weights on the individual terms can bemanually selected, based on empirical evidence or learned-from atraining set.

[0289] General-purpose optimisation methods such as steepest descent,conjugated gradient, quasi-Newton methods, Newton methods, dynamicprogramming, simplex methods, pattern search, generic algorithms,simulated annealing and stochastic diffusion can be applied to determinethe optimal placement Most of the optimisation algorithms are iterativemethods and require an initial configuration, v₀, which is generatedmanually or automatically 2101, see details below. Given a placement v,a collision detection 2104 is performed followed by an evaluation off(v) 2105. If the relative improvement is below a specified threshold,ε, 2106 the algorithm is finished otherwise the placement is updated2207. The main difference between the optimisation methods is the waythe placement is updated 2207, v_(i−1)=g(v_(i)), during theoptimisation.

[0290] An alternative to apply general-purpose optimisation methods isto use pseudo physics for the optimisation. Preferably a simplifiedphysical model of the system is formulated. This pseudo physical modelcan be very powerful for updating of component placement when thecomponent collides with another component or the shell. In practice themodel may be applied to make the colliding component “bounce off” theshell or another component. Classic physics can be used to perform thistype of modelling e.g. combined with approximate surface normals in thecollision regions. Some object function has direct physical modelinterpretations. In this case the full optimisation can be performed inthe physical framework. In most case however the physical modelling iscombined with general-purpose optimisation methods, e.g. by applyingphysics for collisions and otherwise general-purpose, optimisationmethods.

[0291] Penalties may vary over the ear e.g. penetrations in soft partsof the ear obtains a lower penalty than in hard parts of the ear orpenetration of parts of the shell consisting of hard material receivelower penalties than penetration of harder regions. The differentpenalties are obtained by assigning different weights to the relevantparts of the ear. These weights are then multiplied on the initialpenalty corresponding to the same parts of the ear as the weights. Highweights lead to high penalties. In the case of penetrations of hard andsoft parts of the ear, the hard and soft parts of the ear will beassigned high and low weights, respectively. The weights can be input byan operator or obtained automatically from the most similar model in thedatabase. In the case of weights related to anatomical features of theear, the weights can be obtained by a registration of the model to ananatomical atlas from which the weights can be derived. The anatomicalatlas can either be based on a, (single standard ear or differentstandard ears for different groups. The weights can also be determinedbased on the dynamic variation of the ear and especially the ear canalunder different circumstances, e.g. with open and closed mouth. Thedynamics are preferably derived from a set of different models of thesame ear using shape statistics. The set of different models should havebeen captured under different circumstances. An alternative strategy isto modify the reference ear by adding or removing material (see section1.4.17) to change the penalties in the object function.

[0292] A selection tool may also be used to assign different materialsfor the earpiece to different parts of the 3D model. Thus, one problemwith earpieces is that they are exposed to sweat from the surface of theauditory canal and/or the meatus. Parts of the earpiece in contact withthe skin of the wearer can thus be marked and prototyped using aparticularly sweat resistant material, while the other parts are made inanother material, which needs not be sweat resistant The selection ofsuch materials are known to the person skilled in the art of earpiecemanufacturing. Similarly, it may be advantageous to select materials,which are non-allergenic to those parts of the model being in contactwith the skin of the wearer. The selection can be performed by a rulebased approach, according to which surfaces within a certain distancefrom the skin of the wearer are selected.

[0293] For some devices a number of different components exist with thesame 35 functionality, e.g. different transducers. To determine theoptimal component each of the possible components are selected and theplacement is evaluated and optionally optimised using the describedprocedure. The component, which obtains the lowest value of theoptimiser object function, is selected by the system as the bestcomponent. A similar procedure can be used for automated selection ofthe components in the manual approach.

[0294] Initialisation of the component placement is crucial to thesuccess of the later optimisation. Preferably the initialisation isperformed by the similarity-based approach or a feature-based approach,where extracted features are used for positioning. One way to performthe feature-based initialisation is to slice the part of the presentmodel into a number of slices. Preferably these slices haveapproximately the same orientation as the preferred componentorientation e.g. with respect to the canal. Each slice may then beanalysed. This analysis may be performed by examining whether thecomponents or a derived bounding box can be placed approximately insidethe slice. The analysis is usually subject to a number of constraints,e.g. the angle of the components. A slice fulfilling the criteria isthen used for initialisation—typically the slice closest to the canal.Based on the previous analysis the component is placed, e.g. by aligningthe centroid of the component with the centroid of the slice. Moredetails on features can also be found in section

[0295] 1.4 6 Cutting the Visible Part of the Surface

[0296] In close relation with the placement of the component on thevisible surface is usually performed a cutting of the visible part ofthe surface, which removes the unwanted part of the visible surface: Thecutting is performed as described in section 1.4.4. The cutting of thevisible part of the surface using a curve-based cutting tool is shown inFIG. 22.

[0297] Often the components or component surface is used to generate aninitial cutting curve or surface, which can be adjusted by the operator.In some cases the cutting is performed directly by the component surfaceor a curve/surface derived from the components or component surface,e.g. a surface estimate of the component surface shifted in paralleltoward the canal of the model or by-forming a curve from pointsprojected from the component or component surface onto the shellsurface. Alternatively the cutting can be performed more or lessindependently of the component and component surface. If the componentsurfaces and shell surface are not combined during the cutting, the twosurfaces may be connected using the loft operation (see section 1.4.7).

[0298] In the case of the similarity based scheme the cutting tool andposition is directly derived from the most similar model. In the case ofthe rule-based approach the free parameters of the cutting is includedin v and changed to optimise the formulated object function, f(v). Thecutting parameters are usually initialised from the component surfaceand may also be locked to the component surface to reduce the number offree parameters to optimise.

[0299] 1.4.7 Filleting/Lofting

[0300] Filleting is the process of rounding or smoothing an edge. Edgesare undesirable features in earpieces, where smooth and round surfacesin general are preferred. Filleting is illustrated in FIG. 30. Loftingis the process of connecting two surfaces by a new surface. As shownbelow fillet and loft are closely related.

[0301] A very powerful approach to fillet is to remove the triangles3008 in a neighbourhood on and around the edge 3006 and fit a parametricsurface to the neighbourhood of the hole created by the removedtriangles. The surface should preferably be a smooth surface such as a2nd, 3rd or lower order surface, a NURBS surface or another type ofspline surface. New vertices are then sampled on the fitted surface andconnected by triangles. What triangles to remove may be determined byremoving all triangles parts of triangles and/or vertices in a certaindistance from the edge or by directly selecting the proper neighbourhood3003, e.g. limited by two curves 3007, one on each side of the edge, seeFIG. 30. The curves can be manually adjusted by a number of visualcontrol points.

[0302] When the triangles have been removed the fillet usually turnsinto a loft operation, where the boundary of two surfaces need to beconnected. Note that the loft operation in general can be applied toconnect two surfaces. The first step in the illustrated loft operationis to determine correspondence between the vertices 2301 at the twoboundaries 2302, 2303, see FIG. 23. The correspondence may be determinedby an exhaustive search for the correspondence that yields the lowestaverage distance between the corresponding vertices under the constraintthat the order of the vertices is preserved.

[0303] The illustrated loft is based on a cubic B-spline surface, whichrequires a number of control points to be specified. For each vertex iscalculated the vector, v_(c), which is perpendicular to the vertexnormal and the boundary orientation vector in the vertex. The vertexnormal is calculated as the area weighted average of the trianglenormals of the triangles connected to the vertex. For each vertex in theset of corresponding vertices two control points are created as thevertex ±v_(c). An additional control point is then created as v_(c1) andv_(c2) added to the midpoint between the corresponding vertices p₁ andp₂. Beside the created control points the two vertices also act ascontrol points. When this process has been repeated for all sets ofcorresponding vertices, the surface is fully defined by the controlspoints. New vertices are then sampled on the surface, i.e. by samplingthe vertices on the spline, which connect the corresponding vertices.Given these vertices and the ordering of the corresponding vertex sets,the neighbour relationships between the sampled vertices are known.Knowing these relationships makes. K straightforward to connect theneighbouring vertices by triangles. The result of a loft is shown inFIG. 24 and FIG. 30.

[0304] When the fillet/loft has been applied to the model it is notensured that the reference ear model is not penetrated by the connectingsurface 2401, see FIG. 24. This penetration 2402 can however beminimised by moving the control points behind the surface of thereference ear. FIG. 25 shows the reduced penetration 2501 obtained bymoving the additional control point between the corresponding verticesbackward along v_(c1) and v_(c2) until it is behind the surface of thereference ear.

[0305] A number of alternative approaches exist for a fillet operation.The simplest approach to fillet is to apply the smoothing on the edgeand its neighbourhood. Refer to section 1.4.12 for details on smoothing.

[0306] Another approach contracts cylinders with a predefined radius asclose to the edge as possible without letting them pass through thesurface. The surface is then projected onto the cylinders in these areasforming a rounded edge with constant curvature. Alternatively thetriangles in the neighbourhood around the edge can be removed and newvertices can be sampled from the cylinder surface. Note that the radiuscan vary along the edge.

[0307] 1.4.8 Cutting and Filleting of the Canal Part of the Surface

[0308] Like the visible part of the surface a cutting tool is usuallyapplied at the canal part of the surface to remove unwanted portions ofthe surface, see FIG. 30. The cutting can be performed by any of thecutting tools described in section 1.4.4. However the cutting is usuallyperformed by a planar surface 3005, which is also used to close the holeafter the cutting. In the manual approach the operator can select andadjust the cutting tool.

[0309] If the similarity-based approach is applied, the same cuttingtool-and position as applied to the most similar model is used. For therule-based approach the position and orientation of the cutting tool iscombined with the position of the components to be placed on the canalpart of the surface. These free parameters, v, are then optimised withrespect to an object function, f(v), similar to the one used in theplacement of the component on the outer part of the surface, see alsosection 1.4.10.

[0310] Following the cutting a filleting operation 3004 (section 1.4.7)is performed on the cutting edge 3006. i.e. the edge where the cuttingof the model has been performed. FIG. 30 illustrates the full process ofcutting 3001,3002 and filleting 3003,3004 the canal part of the surface.

[0311] 1.4.9 Shelling and Surface Offset

[0312] The original 3D model only consists of, outer surface, but mostfinal 3D models require a shell, so a shelling operation may need to beperformed. FIG. 26 shows a model before shelling 2601 and after shelling2602. The outer shell surface 2603 corresponds to the input surface, soonly an inner shell 2604 needs to be created. The operator defines thethickness of the shell. For many devices it is crucial that a minimumshell thickness is guaranteed.

[0313] An overview of a shelling algorithm is shown in FIG. 27. Thefirst step 2701 in the algorithm is to create a copy of each vertex inthe outer shell surface. FIG. 28 illustrates how the new vertex 2801 onthe inner shell 2802 is created along the scaled normal 2803 of thecorresponding vertex 2804 in the outer shell surface 2805. The vertexnormal 2803 is calculated as the average of the normals of the connectedtriangles weighted by their area. If the minimum shell thickness 2806has to be ensured it is not sufficient to offset the vertex with thespecified shell thickness. However the offset, which locally ensures theshell thickness, can be found as the maximum scale factor, whichprojects the scaled version of the vertex normal onto the full length ofthe triangle normals scaled by the predefined thickness. Only thenormals of the triangles connected to the vertex are of relevance.Unfortunately, the proposed offsetting only ensures a local shellthickness. In areas with convex surfaces and high curvature the offsetvertices tend to violate the minimum shell thickness. These violatingvertices are removed in the second step 2702 to ensure a proper shellthickness. Finally, the new inner shell may then be created by atriangulation 2703 of the created vertices. The triangulation may beperformed using a standard 3D triangulation method such as-proposed byHoppe et al in Surface Reconstruction from unorganised points, ComputerGraphics. 26(2), 1992, pp. 71-78.

[0314] The proposed method may easily be extended to shells with avarying thickness by applying a local thickness in the offsetting of theindividual vertices. Using a selection tool different materials can alsobe assigned to different parts as shown in FIG. 29, where a softermaterial 2901 is assigned to the part of the shell, which corresponds tothe hard or changing part of the ear, e.g. part that changes when themouth is opened and closed: For details on how to assigning differentproperties to different parts of the model refer to section 1.4.5.

[0315] The shelling algorithm may also be used to offset e.g. the outersurface. A small offset of the outer surface may be necessary to ensure,that the final shell has a perfect fit The only difference in applyingthe shelling method for offsetting is that the original model is removedafter the offset-surface is created. Local offsets of parts of the shellcan also be performed. e.g. to create O-rings on the canal part of theshell.

[0316] 1.4.10 Component Placement on the Canal Part of the Surface

[0317] The component placement of the canal part of the surface is veryimportant for a proper functionality of the apparatus and a pleasantinsertion and pleasant use of the apparatus. The canal part of thesurface corresponds to the part of the surface, which is inside theauditory canal. The term components should again be interpreted in abroad sense, e.g. an outlet connected with a tube to a transducer. FIG.31 shows the result of cutting and placement of an outlet 3103 connectedwith a tube 3102 to a transducer 3101.

[0318] Manual Approach

[0319] A flow chart of the manual approach for component placement andthe closely related cutting, lofting and shelling is shown in FIG. 32,Note that this flow chart illustrates the order of the operations usedin FIG. 8, but many different orders of the operations could be applied:see e.g. FIG. 9 or 10. When placing components with multiple parts theparts can be adjusted simultaneously or individually. A component withmultiple parts (outlet tube and transducer) is shown in FIG. 31.Relevant measures such as the length of the tube can be extracteddirectly for later use, e.g. in a manual assembling.

[0320] However, it is usually not sufficient that there is room insidethe shell for the components. The components should also be able toenter this room. This may not be the case if the auditory canal is toonarrow in some parts. To facilitate the placement of components a validpath tool 3206 may be devised for determining the existence of a validpath along which the component is able to move. A minimal path algorithmcombined with collision detection may be applied to determine this path.Depending on the material properties of the components and the shellsome intersection may be allowed. The legal degree of intersection canbe specified, e.g. by the allowed amount of penetration or by theallowed amount of deformation of shell and component, which is requiredto make the component pass. The deformations may need to be modelled.e.g. by finite element models.

[0321] If no valid path exists removal of shell material in collisionregions is possible following section 1.4.17. Collision regions aredefined as the regions, where the component gets stuck. To facilitatethe manual removal of material, the critical region is visualized andthe neighbourhood is marked. However the valid path tool suggests therequired local changes by removing material until the component is ableto pass. These changes can either be accepted by the operator oraccepted automatically under the constraint that the defined absoluteminimum shell thickness is not violated.

[0322] The placement of the components may also be subject to otherconstraints e.g. the angle of the outlet with respect to the ear canal.

[0323] Similarity-Based Approach

[0324] The most similar model is extracted from the database and thesame positions for components are applied. When the components have beenplaced the valid path tool is applied including the automaticmodifications of the local shell thickness—if it is enabled.

[0325] Rule-Based Approach

[0326] The rule-based approach applies the similar methods as therule-based approach for component placement on the visible surface. Themain difference is that a valid path tool may be applied during theoptimisation and invalid configurations are rejected/heavily penalized.A similar type of objet function is also used. However the weights ofthe individual terms in the object function may be changed to fulfil thespecific requirement of the inner surface. Additional terms can also beadded. e.g. the angle of the outlet with respect to the ear canal andthe length of the tube connecting the outlet and transducer.

[0327] Preferably the optimisation of the placement is performed by ageneral-purpose optimisation algorithm by pseudo physics or acombination of both. The initialisation may be performed by thesimilarity-based approach or a feature-based approach, where extractedfeatures are used for placement. One way to perform the feature-basedinitialisation is to slice the canal part of the present model into anumber of slices approximately orthogonal to the local canalorientation. The first slice of the canal, which is reasonably close toorthogonal to the canal surface and approximately able to contain thecomponents optionally including filleting and ventilation channel isapplied for initialization. If a planar cutting is performed on thecanal part, then the initial cutting plane may be identical to theslicing plane. The components may be placed with respect to the centroidand orientation of the slice.

[0328] 1.4.11 Placement of Pressure Ventilation Channel or Sound Bore

[0329] For some devices placed in the ear a pressurecompensation/ventilation channel or a sound bore connecting the insideand the outside of the ear is required to obtain proper performance andpleasant use. FIG. 33 illustrates a model 3301 with a ventilationchannel 3302. Traditionally this channel runs inside the shell, on theinner shell, on the outside or a combination of all.

[0330] Preferably the first step in creating the ventilation channel orsound bore is to determine the exit points on the canal and the visiblepart 3301, 3303 of the surface of the shell a nd the path 3304connecting these points. The skin of the user must not cover the exitpoints and the bending of the channel may be constrained to ensureproper functionality. Further the path of the ventilation channel may beconstrained by a minimum shell thickness, intersection with placedcomponents and a requirement of leaving the outer shell surfaceunchanged.

[0331] Given the exit points and a legal path, the channel may becreated by first adding a solid object, defined along the path, to theinner surface of the present model. The addition and later subtractionmay be performed using a Boolean function, see section 1.4.16. The shapeof the object may be defined by offsetting the specified shape of theventilation channel or sound bore by the minimum shell thickness. In thecase of a tube shaped ventilation channel or sound bore the solid objectmay correspond to a solid tube with a diameter equal to the sum of theventilation channel diameter and the minimum shell thickness. A secondsolid object with the specified shape of the ventilation channel orsound bore defined along the path may be created and subtracted from themodel, creating the final ventilation channel. In the case of a tube thesecond solid object corresponds to a tube with the specified diameter.Note that this method can generate ventilation channels with anarbitrary geometry, e.g. ventilation channels with cross sections of thefollowing types; elliptical/circular, square/rectangular, T-shape,semi-circular with an edge, triangular with an edge, circular/ellipticwith an edge. Ventilation channels with e.g. elliptic shape can make thechannel stay in the shell and increase the space for components etc.Likewise the method facilitates the creation of almost any type of boressuch as large bores, small bores, open bores and fish mouth bores.

[0332] Note that the method describes the generation of a singleventilation channel or sound bore connecting the inner and outersurface. However the approach can easily be generalized to multiplechannels (see FIG. 34) and short channels not necessarily leading thewhole way from the inner to the outer surface. The method can also beused to generate ventilation channels or on the surface by notoffsetting the points. Likewise, the approach can change shape and addextra features like a chamber along the channel by changing the shape ofor adding the feature to the solid object, which is used to create thechannel. FIG. 35 schematically shows a chamber 3501 in the channel. Thechamber is used to improve acoustic properties and reduce pressure.

[0333] The possibility to design ventilation channels or sound boreswith arbitrary shapes and paths, e.g. around the surface, can be appliedto improve the acoustic properties and increase the protection towardsearwax. Acoustic conductors integrated into the shell can also becreated in the same way as the ventilation channels. Finally theacoustic properties of the ventilation channel or sound bore can besimulated and evaluated.

[0334] Manual-Based Approach

[0335] In the manual approach the operator may mark the exit points 3301and a number of ventilation channel control points 3304 on the surfaceto define a sparse sampling of the path. Given these points, acontinuous representation of the path may be created by fitting a curve,e.g. a spline. Before the curve is fitted, the points may be offset fromthe surface to ensure a proper shell thickness. Refer to section 1.4.9for details on offsetting of points. The legality of the path withrespect to intersections with components etc. may be determined usingcollision control and may visually be indicated to support the manualplacement of the channel. If the path is illegal, the operator can movethe individual control points to change the path until a legalconfigurations is obtained. When the points are adjusted the channel maybe simultaneous visualized and illegal parts visually indicated. Newpoints can also be added to define a more precise path

[0336] Similarity-Based Approach

[0337] The most similar model previously extracted from the database maycontain information defining the exit points as well as the pointsspecifying the path. In some cases the viewpoint of the operator(position and orientation) used during the selection of each point isstored with the model. By applying these viewpoints to the presentmodel, the corresponding points on the present model can be obtained.Given the points on the present model the ventilation channel can begenerated.

[0338] An alternative strategy is to project the points from the similarmodel onto the present model to obtain the exit points and the path. Theprojection is performed along the surface normal. By applying theprojected exit points and the path, the ventilation channel is created.

[0339] Rule-Based Approach

[0340] In the automated scheme the exits of the ventilation channel maybe placed given a preferred position. To make the position applicable todifferent models, the position is typically given relative to relevantlandmarks such as surfaces or components. These positions can either beobtained by analysis of a training set or directly inputted by anoperator. Preferably the path is generated using a shortest pathalgorithm, a “water flow” algorithm that determines the most southernpath following the local canal bending or by sub sampling the lineconnecting the exit points and projecting these points onto the shell(following section 1.4.4). All path generation is subject to thepreviously mentioned constraints. Given the exit points and the path thefinal ventilation channel is created.

[0341] In the case no legal path can be generated for the first exitpoints, a number of other exit points may be tested. These points cane.g. be generated from a training set, by an operator or by permutationsof existing points.

[0342] 1.4.12 Optimise Visual Appearance

[0343] The visual appearance is one of the most important properties ofthe earpieces for the users. Hence it is crucial to optimise the visualappearance. Beside the optimisation performed during the previousoperations a number of additional operations may be applied:

[0344] Smoothing or Fairing

[0345] The smoothing or fairing may be performed by a low pass filteringof the model surface followed by ant-shrinkage step. The anti-shrinkagecan be required, because a low pass filtering shrinks convex parts ofthe surface. The low pass filtering may be performed by assigning a newposition equal to the weighted sum of the vertex and its neighbours toeach vertex. One way to perform the anti-shrinkage is to preserve thevolume by scaling the full model. The defined number of iterationscorresponds to the degree of smoothing. The smoothing can either beperformed on the full model or on selected parts.

[0346] Colouring and Texturing

[0347] One of the last actions is to assign colours or texturing to theshell. The colours and the textures can be measured as a part of thescanning process or separately if impressions are scanned. Additionalcolours and textures can be sampled from a standard colour palette and atexture database respectively.

[0348] 1.4.13 Optimise Shell Geometry

[0349] When all components have been placed and all surfacemodifications have been performed, the shell geometry can be, optimised.One objective of the optimisation is to improve the positioning of thecomponents and increase the strength of the shell, see FIG. 36.

[0350] The positioning of the components may be improved by addingholders 3501 or extra material, which fits the exact geometry of thecomponents. Holders such as spikes or rings, may be directly added byBoolean operations, see section 1.4.16 The holders may havevibration-reducing properties. Parts of bounding boxes or componentnegatives can also be used to add extra material, which fits thecomponent. The addition may again be performed using a Boolean addition.

[0351] Adding extra material (see section 1.4.17) also increases theshell strength and compensate for limitations in the physical productionprocess. The strength of the shell can also be improved by increasingthe local shell thickness in non-critical regions as described insection 1.4.9. Grids, ribs, or other features can also be created on theinner shell, e.g. by a projection of the features on the inner shellfollowed by a Boolean addition. Again the objective is-to strengthen andstabilise the shell. All modifications are constrained by collisiondetection and no valid paths are violated.

[0352] For some applications e.g. hearing aids it may be relevant to addextra material on parts of the outer shell surface to make the earpiecefit better and improve acoustics, e.g. by removing feedback. Preferablythese areas are identified by the operator, anatomical knowledge orbased on physical simulations. The addition of extra material isdescribed in section 1.4.17.

[0353] 1.4.14 Creation of Component Locks, Room for Faceplate and/orMultipart Shell

[0354] As one of the last steps the locks for components and/or room forthe faceplate need to be created depending on the particular assemblingprocess.

[0355] Component Locks

[0356] In many applications locks are needed to make it possible toattach and lock the components on the final earpiece—especially if nofaceplate is applied. Examples of locks are operable locks, one-clicklocks or bayonet click locks. These locks may be created by performing aBoolean subtraction (see section 1.4.16) of the negative of thecomponent lock or the component from the present shell. FIG. 37illustrates the creation of a lock 3701 for the electronics.

[0357] Room for Faceplate

[0358] For different reasons many producers still apply a face or coverplate in the assembling, see FIG. 1. The position of the faceplate isdirectly determined by the position of the components on the visiblepart of the surface. To make the assembling with a faceplate possibleroom needs to be created for this faceplate, i.e. the part of the model,which should correspond to the faceplate needs to be cut away. FIG. 38illustrates the final model 3802 after the removal of the faceplate part3803 of the present model. The removal is performed by cutting the modelwith the surface 3801 corresponding to the backside of the faceplatemodel aligned with respect the position of the components. Preferablythe backside of the faceplate presents structures to uniquely positionand lock the shell and faceplate. Examples of such structures are lines,grids or other locks. FIG. 39 illustrates the use of a line structure3903 for locking faceplate and shell.

[0359] When a faceplate is applied modifications of the faceplate needto be computer controlled if the final earpiece should obtain the sameshape as the model before room was made for the faceplate. Themodification of the faceplate may be controlled by supplying the millingpaths for a milling device, which can be applied to modify thefaceplate. The milling paths are generated by offsetting the surfaceoutward with a distance corresponding to the milling head radiusfollowing section 1.4.9. The part of the offsetted surface, whichcorresponds to the faceplate is then sliced using planar surface cuts.For each slice the outer contour is extracted. These contours become themilling paths.

[0360] An alternative to apply a full faceplate is to use a smallinterface module e.g. a small ring containing a lock for the components.This interface module can then be glued to the shell and the componentscan be inserted and removed easily. In the full frame work the interfacemodule is just interpreted as a component, which may be placed togetherwith the other components.

[0361] Multipart Shell

[0362] Another option is to create a multipart shell, i.e. the shell isseparated into two or more parts, which can be locked together. Theseparation of the shell into two or more pieces allows for easyinsertion and replacement of components and reduces the need for largeholes in the shell through which the components can be inserted. Theseparation of the shell into two parts is performed by cutting thepresent model with a single surface, which corresponds to the desiredseparation surface including locks etc. This cutting creates the firstpart. The second part is then created by cutting the present model withthe same surface with swapped orientation. In a similar way more cutsare performed for shells with more than two parts. The separation couldalso be performed using Boolean subtraction.

[0363] 1.4.15 Placement of Unique Identification

[0364] A large number of earpieces may be produced together In order todistinguish the individual earpieces a unique feature foridentification, such as serial number barcode or colour code, need to beplaced on the earpiece. An example of placing identification is shown inFIG. 39. Preferably the identification should either be placed insidethe shell 3901 or on an extra piece of material 3902, which can easilybe removed. In general the identification should be placed such that iteasily can be read automatically, e.g. by a barcode reader or computervision system. If the rapid prototyping device is single-colour, aserial number can be created with 3D characters, which are added orsubtracted to the surface preferably by a Boolean operation, see section1-4.16. For some single-colour rapid prototyping devices it is alsopossible to create identification by double exposure. In the case whereother components are unique for the earpiece, these components can alsobe assigned a unique identification.

[0365] 1.4.16 Boolean Operation

[0366]FIG. 40 shows how a Boolean function can be used to add. A+B. 4003or subtract, A−B. 4004 two models, A 4001 and B 4002 The power of theBoolean function is also illustrated in FIG. 31, where the outlet 3103is created using the Boolean addition of cylinder model followed by aBoolean subtraction of cylinder model with a smaller radius.

[0367] The Boolean algorithm has strong similarities with the surfacecutting and closing function in section 1.4.4. For each intersectingtriangle in model A and B the loop to be triangulated can be determined.Recall that the loop consists of the intersections of the triangle edgesand one or two vertices from the triangle, see FIG. 14. Compared to thecutting and closing function the difference is which vertices in thetriangle to insert in the loop.

[0368] In the case of the addition, A+B, the vertices in the loop shouldbe selected as the vertices above the other model surface for both A andB. In the same way as in the cutting operations the trianglesbelow/behind the other surface are removed and the two surfaces aremerged.

[0369] For subtraction, A−B, the model A is treated in the same way asin addition. The vertices in the loop for triangles in model B areselected as the vertices below the surface A. Finally, the triangles inB above/in front of the surface of model A are removed and the twosurfaces are merged.

[0370] 1.4.17 Add/Remove Material

[0371] Extra material can locally be added or removed. This may beperformed by locally offsetting the surface outwardly or inwardly,respectively. The addition/removal can be based on a single point on thesurface or selection of an area. In the case of a single point thevertices within a specified distance from the points are offsetted as afunction of their distance to the point The relationship between theamount of offset and the distance is controlled by a proper transferfunction, e.g. a Gaussian. The actual offsetting of the individualvertices is performed as described in section 1.4.9.

[0372] If the input is a selected area all the vertices within theselection are offsetted. The amount of offset is calculated based on thedistance from the vertex to the selection boundary combined with aproper transfer function.

[0373] In some cases larger amounts of material need to be added, e.g.if parts of the ear canal is missing, the canal may be extend. In thegeneral case the material to add is preferably extracted from a similaror standard model and added to the model by a Boolean operation. Inspecial cases like the extension of the ear canal it may be advantageousto fit a parametric surface to the neighbourhood of the extension.Additional control of the surface can be obtained by adding a number ofsurface control points, which make the operator freely able to adjustthe shape of the extension.

[0374] 1.4.18 Extracting the most Similar Model from the Database

[0375] The core in the similarity-based approach is to extract the modelwhich is most similar to the present model from the database. Preferablythe first step is to insert the coordinate system in the present modelfollowing section 1.4.3. A number of features are then extracted fromthe model The features should preferably be homological points,distances and angles between homological points, lower order moments,local curvature and other differential-based features. The appliedfeatures should preferably be invariant of position, orientation andscale Together with each original model in the database thecorresponding features are stored. Each model has a corresponding pointin feature space. The candidates for the most similar model are thenextracted as the “nearest neighbours” to the feature point, which isrelated to the present model. Preferably the nearest neighbours aredetermined using the Euclidean or Mahalanobis distance in feature space,neural networks, fuzzy logic or another parametric or non-parametricmodel.

[0376] A registration of the present model and each candidate may thenbe performed and the closest model may be extracted as the most similarmodel. The closest model may be defined with respect to the averageleast square distance between the vertices in the present model andsurface of, the candidate models. The registration may be performedusing the Iterative Closest Point algorithm. (Besi, P. J. and McKay, N.D., “A method for registration of 3D shapes”, IEEE Transaction onPattern 35 Analysis and Machine Intelligence. 17(1), pp. 239-256, 1992).

[0377] 1.4.19 Visualisation and Simulation

[0378] The earpiece and the related components can be visualised fullyidentical to the final product where not just the major components butalso wires, connectors and all other used pieces are included.Simulation may be performed to determine the, influence and movement ofthe transducers, tube, wires etc. when the earpiece is moved such aswhen user is moving or eating. These simulations are preferablyperformed using classical physics and also include mutual interactionThe required physical parameters such as mass and flexibility areassigned to all the individual components. One advantage of the physicalsimulation is the possibility to optimise the size of differentcomponent, e.g. the length of the wire connecting electronic and phone.

[0379] Insertion and removal of the earpiece in the virtual ear may alsobe simulated. This simulation ensures that the earpiece is actually ableto enter the ear. The simulation also includes the amount of deformationand pressure applied to the, ear and earpiece, which is required for theinsertion and removal. The amount and position of the ear deformationand pressure makes is possible to estimate the nuisance caused by theinsertion and removal of the earpiece. Likewise the nuisance can also beestimated when the earpiece is placed in the correct position Againrealistic physical parameters are assigned to the ear and earpiece. Theparameters assigned to the ear may be obtained by a registration of theear to an anatomical atlas.

[0380] Simulations of the acoustic properties of the modelled earpiececan also be performed.

[0381] The full visualisation and physical simulations facilitate themost realistic evaluation of the modelling result and can be used tooptimise the modelling to obtain the overall most satisfying result.

[0382] 1.5 Output of the System

[0383] The final optimal 3D model is then added to the database. Thedatabase has a number of applications, e.g. it can be applied to producenew earpieces using the similarity-based approach, derive shapestatistics used for purposes such as optimal component design andimproved acoustic simulation, perform growth and age modelling of theauditory canal and the rest of the ear, reproduce lost or damagedearpieces and/or create quality reports. A part of the quality reportcan be the amount of penetration of the virtual ear, see FIG. 41.

[0384] The physical version of the final 3D model may be produced usinga rapid prototyping set-up such as Milling, stereo lithography/SLA,solid ground curing, selective laser sintering, direct shell productioncasting, 3D-printing, topographic shell fabrication, fused depositionmodelling, inkjet modelling, laminated object manufacturing,nano-printing or any other system that produces real models from 3Dcomputer models. The final 3D model will be directly saved in a formatcompatible with the manufacturing set-up. Using a packing algorithm alarge-number of 3D models may be optimally positioned in 3D space andmanufactured simultaneously to increase production speed.

[0385] The system is also able to generate post processing instructionsand other derived data e.g. programs or settings for the correspondinghearing aid electronic. When faceplates are used generation ofinstructions for the milling of the faceplate is essential if thecorrect shape should be obtained. These instructions are also stored inthe database and can be downloaded to the milling machine manually orautomatically.

[0386] Instructions for manual or automated assembling are alsogenerated. Preferably these instructions include assemblinginstructions, component specifications and optimal dimensions, e.g. oftubes and wires. One use of these instructions is to automatically,prepare and adjust the components for assembling. Due to the preciseknowledge of the shape the system is also able to create instructionsfor automated assembling of shell, faceplate, electronics and othercomponents. Without this shape knowledge it is basically impossible toperform automated assembling e.g. by a robot, due to the smalldimensions and high requirements for precision. The knowledge of theprecise position of components can also be used to mount componentsbefore or during the production of the shell. The system is also able tooptimise the position and orientation of the shell in the production tofacilitate this placement of components. This makes it possible to buildcomponent into the shell and to mount components that cannot be insertedinto the final shell. Simple components can also be created directly,e.g. printed.

[0387] Most of the handling and processing of earpiece require that theidentity of the present earpiece is known. The earpiece is preferablyidentified automatically, e.g. by a barcode reader or computer visionsystem.

1. A method for computer-assisted modelling of customised earpiecescomprising at least one part being individually matched to an auditorycanal and/or a meatus, said method comprising the steps of: a) obtaininga three-dimensional computer model, 3D-model, of at least part of theauditory canal, said 3D-model having an outer surface, b) initiallyarranging at least one component in relation to the 3D-model, c)initially arranging a cutting curve or cutting surface in relation tothe outer surface of the 3D-model, said cutting curve or surfacedividing the 3D-model in an outer portion and an inner portion, d)initially forming a connecting surface connecting the at least onecomponent and *the inner portion of the 3D-model, said connectingsurface thereby being part of the 3D-model, e) performing an evaluationof the arrangement of the at least one component, said evaluationcomprising a collision detection of the at least one component inrelation to one or more parts of the 3D-model and/or other components,and f) adjusting the arrangement of the at least one component, thearrangement of the cutting curve or surface, and/or the formation of theconnecting surface based on the result of said evaluation.
 2. The methodaccording to claim 1, wherein steps (e) and (f) are repeated until thecollision detection fulfils a required minimum criterion.
 3. The methodaccording to any of the preceding claims, wherein the arrangement of theat least one component, and/or the arrangement of the cutting curve orsurface, and/or the formation of the connecting surface is/are adjusteduntil no collision is detected.
 65. 4. The method according to any ofthe preceding claims, wherein an object function, f(v), is defined forexpressing the quality of the arrangement of the at least one component,and/or the arrangement of the cutting curve or surface. And/or theformation of the connecting surface, said object function being anIncreasing function of the number of detected collisions and beingcalculated for each new arrangement of the at least one component and/orcutting curve or surface, and wherein the arrangement of the at leastone component, and/or the arrangement of the cutting curve or surface,and/or the formation of the connecting surface is/are adjusted until theobject function fulfils a given minimum criterion.
 5. The methodaccording to claim 4, wherein said minimum criterion is that the objectfunction obtains a minimum value, or that the difference in the valuesof two successively determined object functions is below a definedvalue.
 6. The method according to claim 4 to 5, wherein for said objectfunction consists of a weighted sum of terms related to constraints anda number of other terms, which express the quality of the earpiece. 7.The method according to claim 6, wherein the other terms are selectedfrom the group consisting of the volume of the shell, the outer shellsurface, the visible shell surface area, the length of intersectionbetween the reference ear and the cutting surface, the area of thecutting surface after the cut, the maximal penetration of the referenceear by a component, the average of the penetration and the acousticproperties.
 8. The method according to any of the preceding claims,wherein a general purpose optimisation algorithm, psuedo physics or acombination are used to optimise component placement.
 9. The methodaccording to claim 1, wherein the steps are performed in the order a),b), c), d) e), f.
 10. The method according to claim 1, wherein the stepsare performed in the order a), c), b), d), e), f).
 11. The methodaccording to claim 1, wherein the steps are performed in the order a),c), b), e), d), f).
 12. The method according to claim 1 wherein thesteps are performed in the order a), b), e), c), d), f).
 13. The methodaccording to claim 1, wherein the steps are performed in the order a),b), c), e), d), f).
 14. The method according to any of the precedingclaims, wherein the 3D model is obtained by scanning an impression ofthe auditory canal and/or concha and/or meatus and optionally part ofthe outer ear.
 15. The method according to any of the preceding claims,wherein the 3D model is obtained by ultrasound scanning of the auditorycanal and/or concha and/or meatus.
 16. The method according to any ofthe preceding claims, wherein the 3D model is obtained by scanning theauditory canal and/or concha and/or meatus with a 3D structured lightscanner.
 17. The method according to any of the preceding claims,wherein the 3D model is obtained by CT and/or MRI and/or MR scanning ofthe auditory canal and/or concha and/or meatus.
 18. The method accordingto any of the preceding claims 14 to 17, wherein the scanning furthercomprises a texture scan, including a colour scan.
 19. The methodaccording to any of the preceding claims, comprising a further stepduring which holes in the 3D model are closed.
 20. The method accordingto any of the preceding claims, comprising a further step during whichdefects are removed from the 3D model.
 21. The method according to claim20, wherein defects areas selected from the group consisting of thethread used for removing the impression, artefacts, scars, earwax,tissue, and hair.
 22. The method according to any of the precedingclaims further comprising, removing unwanted parts of the 3D modelsurface.
 23. The method according to claim 22, whereby unwanted partsare removed using a cutting curve/surface.
 24. The method according toclaim 22, whereby unwanted parts are removed by marking the parts on the3D-model.
 25. The method according to any of the preceding claims,comprising a further step during which a second cutting surface/curve isarranged in relation to the outer surface of the 3D model.
 26. A methodaccording to any of the preceding claims, wherein the arrangement of theat least one component in relation to the 3D-model comprises arranging acomponent surface of the at least one component in relation to the3D-model.
 27. The method according to claim 26, wherein a connectingsurface is connecting said component surface and said inner portion ofthe 3D-model.
 28. The method according to any of the preceding claims,wherein said initial arrangement of the at least one component inrelation to the 3D-model comprises arranging at least part of the atleast one component substantially at the interior of the 3D-model. 29.The method according to any of the preceding claims, wherein saidevaluation includes an evaluation of the arrangement of the cuttingcurve or surface and/or the connecting surface.
 30. The method accordingto claim 29, wherein the evaluation includes a visual evaluation of thearrangement and/or an acoustic evaluation and/or an evaluation of thefit in relation to a virtual ear.
 31. The method according to any of thepreceding claims, wherein the formation of the connecting surface iscomputer controlled or computer assisted.
 32. The method according toany of the preceding claims, wherein the formation of the connectingsurface comprises a lofting process.
 33. The method according to claim32, wherein the lofting process comprises fitting a parametric surfaceto the boundary of the inner portion of the 3D-model and to the boundaryof a surface defining an outer boundary of said at least one componentin relation to the 3D-model.
 34. The method according to any of thepreceding claims, wherein the formation of the connecting surfacecomprises a filleting process of the edge or boundary of the innerportion of the 3D-model.
 35. The method according to claim 34, whereinthe outer shell surface of the 3D-model is given in a vertexrepresentation with the vertices being connected by triangles, and thefilleting process comprises removing at least part of the triangles in aneighbourhood around at least part of said edge and fitting a parametricsurface to the neighbourhood of the hole created by the removedtriangles.
 36. The method according to claim 33 or 35, wherein theparametric surface comprises a cubic B-spline surface.
 37. The methodaccording to claim 34, wherein filleting comprises smoothing on the edgeand its neighbourhood.
 38. The method according to any of the pr cedingclaims, wherein at least part of the inner portion of the 3D-model isshelled, said shelled inner portion having an inner and another shellsurface.
 39. The method according to claim 38, wherein the shell of the3D-model is generated by a shelling process being computer controlled orcomputer assisted.
 40. The method according to any of the claims 38 to39, wherein the shell of the 3D-model has a predetermined minimum shellthickness.
 41. The method according to any of the claims 38 to 40,wherein the at least partly shelled 3D-model Is obtained from athree-dimensional computer model, 3D-model, of at least part of theauditory canal, said 3D-model having an outer shell surface beingparameterised by a number of vertices, which vertices are connected bytriangles, said shelling process comprising: offsetting inwardly a copyof each vertex in the outer shell surface, removing the number of copiedvertices being closer to the outer shell surface than a given minimumshell thickness, and creating an inner shell by triangulation of theremaining copied vertices.
 42. The method according to claim 41, whereinthe size of the offset varies over the surface.
 43. The method accordingto any of the claims 38 to 41, wherein the inner shell surface orgeometry of the 3D-model is modified in order to improve the strength ofthe finished shell, said modification comprising adding extra materialto at least part of the inner surface of the shell, while at the sametime avoiding collision between the modified inner shell surface and thearranged components.
 44. The method according to any of the precedingclaims, wherein adding or removal of material to the inner shell surfaceof the 3D-model is performed using a Boolean operation, such as aBoolean addition/subtraction.
 45. The method according to any of thepreceding claims, wherein adding or removal of material in an areacomprises selection of a point and the amount of offset is a function ofthe distance from the point, such as a Gaussian function.
 46. The methodaccording to any of the preceding claims, further comprising a processcomprising an outward offset on at least part of the outer shell surfaceof a 3D computer model, said 3D model having an outer shell surfacebeing parameterised by a number of vertices, which vertices areconnected by triangles, said process comprising outwardly offsetting acopy of each vertex in the outer shell surface, and removing the numberof copied vertices being closer to the outer shell surface than a givenminimum distance, and creating a new offset surface by triangulation ofthe remaining copied vertices.
 47. The method according to claim 46,further comprising a lofting process to connect the offset part(s) tothe non-offset part(s).
 48. The method according to any of the precedingclaims; wherein an anatomical atlas is used to map soft and hard partsof the auditory canal and/or concha and/or meatus to the model
 49. Themethod according to claim 48, wherein models are grouped to differentanatomical atlases by selecting the atlas being most similar to themodel.
 50. The method according to any of the preceding claims 48 to 49,wherein different materials are assigned to different parts of the modeltaking the location of hard and soft parts into consideration.
 51. Themethod according to any of the preceding claims, wherein differentmaterials are assigned to different parts of the model taking theacoustic properties of the materials into consideration.
 52. The methodaccording to any of the preceding claims, wherein different materialsare assigned to different parts of the model taking the allergenicproperties of the materials into consideration.
 53. The method accordingto any of the preceding claims, wherein sweat resistant materials areassigned to the part of the models exposed to sweat.
 54. The methodaccording to any of the preceding claims, wherein materials of differentcolour are assigned to different parts of the model in order to create avisual label or tag on the model and/or to improve the visual appearanceof the model.
 55. The method according to any of the preceding claims,wherein the inner portion of the 3D-model at least partly comprises arepresentation of a model of an earpiece.
 56. The method according toany of the preceding claims, wherein the outer portion of the 3D-modelat least partly comprises a model of a virtual ear.
 57. The methodaccording to claim 56, wherein said virtual ear is connected to a 3Dhead model.
 58. The method according to claim 57, wherein the 3D headmodel is a model of the user or a dummy 3D head model.
 59. The methodaccording to any of the preceding claims, wherein the collisiondetection includes a collision detection of a component surface inrelation to one or more parts of the 3D-model.
 60. The method accordingto any of the preceding claims, wherein the collision detection of thecomponents includes a collision detection of the mutual arrangement ofthe components themselves.
 61. The method according to any of thepreceding claims, wherein said one or more parts of the 3D-model inrelation to which the collision detection may be performed comprises atleast part of the inner portion and/or at least part of the outerportion of the 3D-model.
 62. The method according to claim 59, whereinsaid one or more parts of the 3D-model in relation to which thecollision detection may be performed comprises at least part of theinner shell surface.
 63. The method according to claim 56 and 59,wherein said one or more parts of the 3D-model in relation to which thecollision detection may be performed comprises at least part of an innersurface of the virtual ear.
 64. The method according to any of thepreceding claims, wherein said collision detection is performed usingvarying penalties for different parts of the 3D model.
 65. The methodaccording to claim 64, wherein the different parts of the 3D modelcomprise representations of soft and hard parts of the auditory canal.66. The method according to any of the preceding claims, wherein saidcollision detection is performed by inspection of the three-dimensionalcomputer model, 3D-model.
 67. The method according to any of the claims1 to 65, wherein said collision detection is computer-controlled orcomputer-assisted.
 68. The method according to any of the precedingclaims, wherein the component and/or component surface is used togenerate the initial cutting curve/surface.
 69. The method according toclaim any of the preceding claims, wherein initial cutting is performedby the component surface.
 70. The method according to claim any of thepreceding claims, wherein initial cutting is performed by acurve/surface derived from the component surface.
 71. The methodaccording to any of the preceding claims 1 to 67, wherein the initialcutting curve/surface is generated without the component or componentsurface.
 72. The method according to any of the preceding claims,wherein the initial cutting curve/surface is marked on an impressionbefore scanning said impression and said marking is used to generate theinitial cutting curve/surface.
 73. The method according to any of thepreceding claims, wherein said initial arrangement of the at least onecomponent and/or the cutting curve or surface is performed manually. 74.The method according to any of the preceding claims, said initialarrangement of the at least one component and/or the cutting curve orsurface is performed using a feature-based approach, in which featuresextracted from the obtained 3D-model is used for the arrangement. 75.The method according to claim 74, whereby texture marked on theimpression used to generate the 3D-model is used for initialarrangement.
 76. The method according to claim 74, comprising slicing atleast part of the model into slices, selecting a slice fulfilling anumber of constraints, and using this slice for initial-placement of theat least one component.
 77. The method according to any of the precedingclaims, wherein said initial arrangement of the at least one componentand/or the cutting curve or surface is performed using asimilarity-based approach, in which the obtained 3D-model is compared toa number of stored 3D-models of previously generated optimised models.78. The method according to any of the preceding claims, wherein saidinitial arrangement of the at least one component and/or the cuttingcurve or surface is performed based on mirroring from the optimisedother ear of the-same person.
 79. The method according to any of thepreceding claims, wherein said initial arrangement of the at least onecomponent and/or the cutting curve or surface is performed based on anearlier optimised model from the same person.
 80. The method accordingto claim 77, wherein a stored optimised 3D-model is selected as the mostsimilar 3D-model and the initial arrangement of the at least onecomponent and/or cutting curve or surface is selected substantiallyequal t6 the optimised arrangement of the at least one component and/orcutting curve or surface of said most similar 3D-model.
 81. The methodaccording to any of the claims 77 to 80, wherein said comparison of3D-models and selection of the most similar 3D-model iscomputer-controlled or computer-assisted.
 82. The method according toany of the claims 80 to 81, wherein said selection of initialarrangements of the at least one component and/or cutting curve orsurface is computer-controlled or computer-assisted.
 83. The methodaccording to any of the preceding claims, wherein said adjustment(s) ofthe arrangement of the at least one component and/or the cutting curveor surface is performed manually.
 84. The method according to any of theclaims 1 to 82, wherein said adjustment(s) of the arrangement of the atleast one component, and/or the arrangement of the cutting curve orsurface, and/or the formation of the connecting surface iscomputer-controlled or computer-assisted.
 85. The method according toany of the preceding claims, said method further comprising arrangementof components at the Interior or inner surface of the inner portion ofthe 3D-model.
 86. The method according to claim 85, wherein thearrangement of components at the interior or inner surface is optimisedusing a general purpose optimisation algorithm, by psuedo physics orusing a combination of both.
 87. The method according to any of thepreceding claims, further comprising the arrangement of ribs on theinner and/or outer surface of the 3D-model.
 88. The method according toany of the preceding claims, further comprising arrangement of holderssuch as spikes and/or rings and/or adding of extra material to themodel.
 89. The method according to any of the claims 85 to 87, whereinsaid arrangement of components at the interior or inner surface and/orarrangement of holders and/or adding of extra material and/orarrangement of ribs is manual.
 90. The method according to any of theclaims 85 to 87, wherein said arrangement of components at the interioror inner surface and/or arrangement of holders and/or adding of extramaterial and/or arrangement of ribs is computer controlled, such assimilarity based or ruled based.
 91. The method according to any of theclaims 85 to 87, wherein said arrangement of components at the interioror inner surface and/or arrangement of holders and/or adding of extramaterial and/or arrangement of ribs is computer assisted.
 92. The methodaccording to any of the preceding claims, wherein at least part of thecomponents are selected from a list of components comprising: electroniccomponents, outlets to interior components, tubes, ventilation channel,amplifier, microphone, vibration pick-up, microchip, transducer,wireless communication/identification devices, position sensors such asGPS, loudspeaker, tubes, battery, printed circuits, faceplate, surfacepatches, inlets, outlets, wires, conductors, volume controls, nail grip,extraction cord, tele coil, locking means, interface modules,identification and logo.
 93. The method according to any of thepreceding claims, wherein at least one component is arranged in a plate.94. The method according to claim 93, wherein the component is fixed inthe plate by a component lock.
 95. The method according to claim 94,wherein the component lock is a bayonet, a one-click lock or an operablelock.
 96. The method according to claim 93, wherein the backside of theplate comprises structures to lock the plate to the 3D model.
 97. Themethod according to claim 93, wherein the backside of a model of theplate is used for the initial cut of the 3D model.
 98. The methodaccording to claim 93, further comprising cutting a 3D-model of theplate with the outer surface of the 3D model.
 99. The method accordingto any of the preceding claims, said method further comprisingarrangement of a ventilation channel at the interior or inner surface ofthe inner portion of the 3D-model.
 100. The method according to claim99, comprising arranging exit points on the canal part and the visiblepart of the 3D model.
 101. The method according to claim 99, wherein thechannel is created by adding a solid object defined along a path betweenthe exits to the inner shell surface of the model.
 102. The methodaccording to claim 101, further comprising subtracting an object havingthe shape of the ventilation channel.
 103. The method according to claim99, wherein the channel is created by adding a hollow object definedalong a path between the exits to the inner shell surface of the model.104. The method according to claim 99, wherein the ventilation channelis arranged on the outer surface of the model.
 105. The method accordingto any of the preceding claims, comprising arrangement of furtherchannels in the 3D model, such as a large bore (horn effect), a smallbore (reverse horn effect), an open bore, a fishmouth bore (bell bore),an angle vent, an external vent, a parallel vent or a mini vent plug.106. The method according to any of the preceding claims 99 to 105,wherein ventilation channels and/or sound bores are applied to improvethe acoustic properties and/or to increase the protection againstearwax.
 107. The method according to any of the preceding claims 99 to105, wherein the cross section is circular or elliptical orsquare/rectangular or T-shaped, or semi-circular with an edge, ortriangular with an edge or circular/elliptical with an edge.
 108. Themethod according to any of the claims 99 to 105, wherein saidarrangement of channels is manual.
 109. The method according to any ofthe claims 99 to 105, wherein said arrangement of channels is computerassisted.
 110. The method according to any of the claims 99, to 105,wherein said arrangement is of channels computer controlled, suchas-similarity based or rule based.
 111. The method according to claim110, wherein said arrangement is based on a shortest path algorithmand/or a “water flow” algorithm.
 112. The method according to any of thepreceding claims, said method further comprising an optimisation of thevisual appearance.
 113. The method according to claim 112, comprisingsmoothing or fairing by low 30 pass filtering of the model surfacefollowed by an anti-shrinkage step.
 114. The method according to claim112, comprising assigning colours and/or texturing to the surface of theshell.
 115. The method according to any of the preceding claims, saidmethod further comprising placement of a unique identifier at the innerportion of the 3D-model.
 116. The method according to claim 115, whereinthe unique identifier comprises a barcode or another computer readabletag.
 117. The method according to any of the preceding claims, whereinthe optimised 3D model is divided into two or more parts by arrangingone or more further cutting surfaces.
 118. The method according to anyof the preceding claims, further comprising visualisation of theoptimised model.
 119. The method according to any of the precedingclaims, further comprising production of a difference map illustratingthe difference between the original 3D model and the optimised 3D model.120. The method according to any of the preceding claims, furthercomprising acoustic modelling of the 3D model.
 121. The method accordingto any of the preceding claims, further comprising generation ofassembly instructions.
 122. The method according to any of the precedingclaims, further comprising prototyping and assembly of the earpiece.123. The method according to claim 122, wherein the assembly is manual.124. The method according to claim 122, wherein the assembly isperformed by a robot being controlled by instructions generated by thecomputer.
 125. The method according to any of the preceding claims,further comprising generation of instructions for milling a faceplace,and computer-controlled milling of the faceplate.
 126. A method forcomputer-assisted modelling of customised earpieces comprising at leastone part being individually matched to an auditory canal and/or ameatus, said method comprising the steps of: a) obtaining athree-dimensional computer model, 3D-model, of at least part of theauditory canal, said 3D-model having an outer surface, b) initiallyarranging at least one component in relation to the 3D-model, c)initially arranging a cutting curve or cutting surface in relation tothe outer surface of the 3D-model, said cutting curve or surfacedividing the 3D-model in an outer portion and an inner portion, d)initially forming a closing surface closing the hole partly orcompletely created in the 3D-model by the cutting curve/cutting surface,e) performing an evaluation of the arrangement of the at least onecomponent, said evaluation comprising a collision detection of the atleast one component in relation to one or more parts of the 3D-modeland/or other components, and adjusting the arrangement of the at leastone component, the arrangement of the cutting curve or surface, and/orthe formation of the connecting surface based on the result of saidevaluation.
 127. The method of claim 126, further comprising any of thefeatures of any of claims 2 to
 125. 128. A method for computer-assistedmodelling of customised earpieces comprising at least one part beingindividually matched to an auditory canal, said method comprising thesteps of: obtaining a three-dimensional computer model, 3D-model of atleast part of the auditory canal, said 3D-model having an outer surface,initially arranging a at least one component in relation to the3D-model, initially arranging a cutting curve or cutting surface inrelation to the outer surface of the 3D-model, said cutting curve orsurface dividing the 3D-model in an outer portion and an inner portion,said initial arrangement of the at least one component and/or cuttingcurve or surface being performed using a similarity-based approach, inwhich the present obtained 3D-model Is compared to a number of storedmodels of previously generated optimised 3D-models, with one of saidstored 3D-models being selected as the most similar model and theinitial arrangement of the at least one component and the cutting curveor surface being set substantially equal to the optimised arrangementsof the at least one component and the cutting curve or surface of saidmost similar 3D-model.
 129. The method according to claim 128, whereinsaid comparison of the present 3D-models and selection of the mostsimilar 30-model is computer controlled or computer assisted.
 130. Themethod according to claim 128 or 129, wherein said selection of initialarrangement of the at least one component and the cutting curve orsurface is computer controlled or computer assisted.
 131. The methodaccording to any of the claims 128 to 130, said method furthercomprising the step of initially forming a connecting surface connectingthe at least one component and the inner portion of the 3D-model, saidconnecting surface thereby being part of the 3D-model.
 132. The methodaccording to any of the claims 128-131, wherein the present 3D-model andthe stored previously optimised 3D-models have an outer shell surfacebeing parameterised by a number of vertices, which vertices areconnected by triangles, and said selection of the most similar 3D-modelcomprises: extracting a number of features from the present 3D-model,comparing said number of extracted features with corresponding storedfeatures of a number of stored 3D-models, and selecting a number ofstored 3D-models as candidates for the most similar 3D-model, saidcandidates being the stored 3D-models having the compared features beingnearest neighbours, In a feature space, to the feature points of thepresent 3D-model.
 133. The method according to claim 132, said methodfurther comprising: registration of the present 3D-model and theselected candidate 3D-models, selection of the most similar 3D-model asthe model of candidate ˜3D-models having the smallest distance betweenthe outer shell surface of said candidate 3D-model and the outer shellsurface of the present 3D-model.
 134. The method of claim 128, furthercomprising any of the features of any of claims 2 to
 125. 135. A methodfor computer-assisted modelling of customised earpieces comprising atleast one part being individually matched to an auditory canal, saidmethod comprising the steps of: obtaining a three-dimensional computermodel, 3D-model, of at least part of the auditory canal, said 3D-modelhaving an outer surface, initially arranging a at least one component inrelation to the 3D-model, initially arranging a cutting curve or cuttingsurface in relation to the outer surface of the 3D-model, said cuttingcurve or surface dividing the 30-model in an outer portion and an innerportion, said initial arrangement of the at least one component and/orcutting curve or surface being performed using a feature-based approach,in which features extracted from the obtained 3D-model are used for thearrangement.
 136. A computer program product including a computerreadable medium, said computer readable medium having a computer programstored thereon, said program for causing computer-assisted modelling ofcustomized earpieces comprising at least one part being individuallymatched to an auditory canal, said program comprising: program code forcausing a computer to obtain a three-dimensional computer model,30-model, of at least part of the auditory canal, said 3D-model havingan outer surface, program code for causing a computer to initiallyarrange at least one component in relation to the 3D-model, program codefor causing a computer to Initially arrange a cutting curve or cuttingsurface in relation to the outer surface of the 3D-model, said cuttingcurve or surface dividing the 3D-model in an outer portion and an innerportion, program code for causing a computer to initially form aconnecting surface connecting the at least one component and the innerportion of the 3D-model, said connecting surface thereby being part ofthe 3D-model, program code for causing a computer to perform anevaluation of the arrangement of the at least one component saidevaluation comprising a collision detection of the at least onecomponent in relation to one or more parts of the 3D-model, and programcode for causing a computer to adjust the arrangement of the at leastone component, the arrangement of the cutting curve or surface, and/orthe formation of the connecting surface based on the result of saidevaluation.
 137. The computer program product according to claim 136, inthe physical form of a hard disc, a floppy disc, a magnetic datacarrier, a ZIP, a smart card, a CD ROM, or a DVD.
 138. The computerprogram product according to claim 136, further comprising program codefor ca using a computer to perform any of the steps of any of themethods of claims 2 to
 125. 139. A computer data signal embodied in asignal wave, said computer data signal including a computer program saidprogram for causing computer-assisted modelling of customised earpiecescomprising at least one part being individually matched to an auditorycanal, said program comprising: program code for causing a computer toobtain a three-dimensional computer model, 3D-model, of at least part ofthe auditory canal, said 3D-model having an outer surface, program codefor causing a computer to initially arrange at least one component inrelation to the 3D-model, program code for causing a computer toinitially arrange a cutting curve or cutting surface in relation to theouter surface of the 3D-model, said cutting curve or surface dividingthe 3D-model in an outer portion and an inner portion, program code forcausing a computer to initially form a connecting surface connecting theat least one component and the inner portion of the 3D-model, saidconnecting surface thereby being part of the 3D-model, program code forcausing a computer to perform an evaluation of the arrangement of the atleast one component, said evaluation comprising a collision detection ofthe at least one component in relation to one or more parts of the3D-model; and program code for causing a computer to adjust thearrangement of the at least one component, the arrangement of thecutting curve or surface, and/or the formation of the connecting surfacebased on the result of said evaluation.
 140. The computer data signalaccording to claim 139, further comprising program code for causing acomputer to perform any of the steps of any of the methods of claims 2to
 125. 141. A system for computer-assisted modelling of customisedearpieces, said system including computer readable memory having one ormore computer instructions stored thereon, said instructions comprisinginstructions operative to cause the computer to obtain athree-dimensional computer model, 3D-model, of at least part of theauditory canal said 3D-model having an outer surface, instructionsoperative to cause the computer to initially arrange at least onecomponent in relation to the 3D-model, instructions operative to causethe computer to initially arrange a cutting curve or cutting surface inrelation to the outer surface of the 3D-model, said cutting curve orsurface dividing the 3D-model in an outer portion and an inner portion,instructions operative to cause the computer to initially form aconnecting surface connecting the at least one component and the innerportion of the 3D-model said connecting surface thereby being part ofthe 3D-model, instructions operative to cause the computer to perform anevaluation of the arrangement of the at least one component, saidevaluation comprising a collision detection of the at least onecomponent in relation to one or more parts of the 3D-model, andinstructions operative to cause the computer to adjust the arrangementof the at least one component, the arrangement of the cutting curve orsurface, and/or the formation of the connecting surface based on theresult of said evaluation.
 142. The system according to claim 141,comprising a 3D scanner, a computer and a computer controllable rapidprototyping machine.
 143. The system according to claim 142, wherein therapid prototyping machine is capable of performing 3D milling and/orstereo lithography/SLA and/or solid ground curing and/or selective lasersintering and/or direct shell production casting and/or 3D-printingand/or topographic shell fabrication and/or fused deposition modellingand/or inkjet modelling and/or laminated object Manufactuability and/ornano-printing.
 144. The system according to claim 142; wherein thescanner and/or the prototyping machine are connected to the computer viaa local area network.
 145. The system according to claim 142, whereinthe scanner and/or the prototyping machine are connected to the computervia the internet.
 146. The system according to claim 142, wherein the 3Dscanner the computer and the rapid prototyping machine are placed in thesame locality.
 147. The system according to claim 142, wherein thecomputer is placed at a “modelling site”.
 148. The system according toclaim 142, wherein the rapid phototyping machine is placed at a “rapidprototyping site”.
 149. The system according to claim 142, wherein the3D scanner is placed by an audiologist or an otologist.
 150. The systemaccording to any of claims 141 to 149, further comprising a database,wherein scan data are stored.
 151. The system according to any of claims141 to 150, comprising a further database, wherein 3D data forcustomised earpieces are stored.
 152. The system according to any ofclaims 150 to 151 wherein the data are stored together with informationidentifying the users of the customised earpieces.
 153. The systemaccording to any of claims 141 to 152, comprising a further database,wherein 3D data for components from different manufacturers are stored.154. The system according to any of claims 141 to 153, furthercomprising a spaceball™ tracking device to assist in manual or computerassisted modelling.
 155. The system according to any of claims 141 to154, further comprising stereo glasses to assist in manual inspection of3D computer screen models.
 156. The system according to any of claims141 to 155, further comprising a robot for automatic assembly of theearpiece.
 157. A method for shelling a 3D model, said method comprisingthe steps of: obtaining a three-dimensional computer model, 3D-model, ofat least part of the auditory canal, said 3D-model having an outer shellsurface being parameterised by a number of vertices, which vertices areconnected by triangles, and performing a shelling process to obtain ashelled 3D-model of at least part of the auditory canal, said shellingprocess comprising: offsetting inwardly a copy of each vertex in theouter shell surface, removing the number of copied vertices being closerto the outer shell surface than a given minimum shell thickness, andcreating an inner shell by triangulation of the remaining copiedvertices.
 158. A computer program product including a computer readablemedium, said computer readable medium having a computer program storedthereon, said program for causing computer-assisted shelling of a 3Dmodel, said program comprising: program code for causing a computer toobtain a three-dimensional computer model, 3D-model, of at least part ofthe auditory canal, said 3D-model having an outer shell surface beingparameterised by a number of vertices, which vertices are connected bytriangles, and program code for causing a computer to perform a shellingprocess to obtain a shelled 3D-model of at least part of the auditorycanal, said shelling process comprising: program code for causing acomputer to offset inwardly a copy of each vertex in the outer shellsurface, program code for causing a computer to remove the number ofcopied vertices being closer to the outer shell surface than a givenminimum shell thickness, and program code for causing a computer tocreate an inner shell by triangulation of the remaining copied vertices.159. A computer data signal embodied in a signal wave, said computerdata signal including a computer program, said program for causingcomputer-assisted shelling of a 3D model, said program comprising:program code for causing a computer to obtain a three-dimensionalcomputer model, 3D-model, of at least part of the auditory canal, said3D-model having an outer shell surface being parameterised by a numberof vertices, which vertices are connected by triangles, and program codefor causing a computer to perform a shelling process to obtain a shelled3D-model of at least part of the auditory canal, said shelling processcomprising: program code for causing a computer to offset inwardly acopy of each vertex in the outer shell surface, program code for causinga computer to remove the number of copied vertices being closer to theouter shell surface than a given minimum shell thickness, and programcode for causing a computer to create an inner shell by triangulation ofthe remaining copied vertices.
 160. A system for computer assistedshelling of a 3D-model said system including computer readable memoryhaving one or more computer instructions stored thereon, saidinstructions comprising: instructions operative to cause the computer toobtain a three-dimensional computer model, 3D-model, of at least part ofthe auditory canal, said 3D-model having an outer shell surface beingparameterised by a number of vertices, which vertices are connected bytriangles, and instructions operative to cause the computer to perform ashelling process to obtain a shelled 3D-model of at least part of theauditory canal, said shelling process comprising: instructions operativeto cause the computer to offset inwardly a copy of each vertex in theouter shell surface, instructions operative to cause the computer toremove the number of copied vertices being closer to the outer shellsurface than a given minimum shell thickness, and instructions operativeto cause the computer to create an inner shell by triangulation of theremaining copied vertices.